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LIBRARY OF CONGRESS. 

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Shelf *5Jq.2j 

UNITED STATES OF AMERICA. 





SAMUEL W. JOHNSON, M. A. 



HOW CROPS GROW. 

A TREATISE ON THE 

CHEMICAL COMPOSITION, STRUCTURE 
AND LIFE OF THE PLANT, 

FOE STUDENTS OF AGRICULTURE. 

WITH 



NUMEROUS ILLUSTRATIONS AND TABLES 




y£* 




SAMUEL W. JOHNSON, M. A., 



PROFESSOR OF THEORETICAL AND AGRICULTURAL CHEMISTRY IX THE SHEF- 
FIELD SCIENTIFIC SCHOOL OF YALE UNIVERSITY J DIRECTOR OF 
THE CONNECTICUT AGRICULTURAL EXPERIMENT STATION; 
MEMBER OF THE NATIONAL ACADEMY OF SCIENCES. 



-:o:- 



NEW YORK: 

ORANGE JUDD COMPANY, 

751 BROADWAY. 



Entered, according to Act of Congress, in the year 1890, by the 

ORANGE JUDD COMPANY, 

In the Office of the Librarian of Congress, at Washington. 










PREFACE. 

:o: 

The original edition of this work, first published in 
1868, was the result of studies undertakenin preparing 
instruction in Agricultural Chemistry which the Author 
has now been giving for three and thirty years. To- 
gether with the companion volume, "How Crops Feed," 
it was intended to present concisely but fully the then 
present state of Science regarding the Nutrition of the 
higher Plants and the relations of the Atmosphere, 
Water, and the Soil, to Agricultural Vegetation. Since 
its first appearance, our knowledge of the subject treated 
of in the present volume has largely participated in the 
remarkable advances which have marked all branches of 
Science during the last twenty years and it has been the 
writers' endeavor in this revised edition to post the book 
to date as fully as possible without greatly enlarging its 
bulk or changing its essential character. In attempting 
to reach this result he has been doubly embarassed, first, 
by the great and rapidly increasing amount of recent 
publications in which the materials for revision must be 
sought, and, second, by the fact that official duties have 
allowed very insufficient time for a careful and compre- 
hensive study of the literature. In conclusion, it is 
hoped that while the limits of the book make necessary 
the omission of a multitude of interesting details, little 
has been overlooked that is of real importance to a fair 
presentation of the subjects discussed, 
in 



TABLE OF CONTENTS. 



Introduction 1 

DIVISION I.— CHEMICAL COMPOSITION OF THE PLANT. 

Chap. I.— The Volatile Part of Plants 12 

§ 1. Distinctions and Definitions . . 12 

§ 2. Elements of the Volatile Part of Plants 14 

§ 3. Chemical Affinity 29 

§4. Vegetable Organic Compounds or Proximate Elements 36 

1. Water 37 

2. Carbhydrates 39 

3. Vegetable Acids 75 

4. Fats 83 

5. Albuminoids and Ferments 87 

6. Amides 114 

7. Alkaloids 120 

8. Phosphorized Substances 122 

Chap. II.— The Ash of Plants 126 

§ 1. Ingredients of the Ash 126 

Non-metallic Elements 127 

Carbon and its Compounds 128 

Sulphur and its Compounds 129 

Phosphorus and its Compounds 132 

Chlorine and its Compounds 132 

Silicon and its Compounds 134 

Metallic Elements . . 138 

Potassium and its Compounds 138 

Sodium and its Compounds 139 

Calcium, and its Compounds 139 

Magnesium and its Compounds 140 

Iron and its Compounds -. 141 

Manganese and its Compounds 142 

Salts 143 

Carbonates 144 

Sulphates 146 

Phosphates 147 

Chlorides 149 

Nitrates 149 

§ 2. Quantity, Distribution, and Variations of the Ash 151 

Table of Proportions of Ash in Vegetable Matter — 152 

§ 3. Special Composition of the Ash of Agricultural Plants 161 

1. Constant Ingredients 161 

2. Uniform composition of normal specimens of 

given plants 161 

Table of Ash-analyses 164 

3. Composition of Different parts of Plant 171 

4. Like composition of similar plants 173 

5. Variability of ash of same species 174 

6. What is normal composition of the ash of a plant? 177 

7. To what extent is each ash-ingredient essential 

or accidental 180 

Water-culture 180 

Essential ash-ingredients 186 

Is Sodium Essential to Agricultural Plants ? 186 

Iron indispensable 192 

Manganese unessential 193 

Is Chlorine indispensable ? 194 

Silica is not essential 197 

Ash-ingredients taken up in excess 201 

Disposition of superfluous matters 203 

State of Ash-ingredients in plant 207 

44. Functions of the Ash-ingredients 210 
1. Quantitative Relations among the Ingredients of 

Plants 220 

§ 2. Composition of the plant in successive stages of 

growth 222 

Composition and Growth of the Oat Plant : 223 

V 



VI TABLE OF CONTEXTS. 



DIVISION II.— THE STRUCTURE OF THE PLANT AND OFFICES 
OF ITS ORGANS. 

Chap. I.— Generalities 241 

Organism, Organs 242 

Chap. II.— Primary Elements of Organic Structure 243 

§ 1. The Vegetable Cell 243 

§ 2. Vegetable Tissues 254 

Chap. III.— Vegetative Organs 256 

§ 1. The Root 256 

Offices of Root 260 

Apparent Search for Food 263 

Contact of Roots with Soil 266 

Absorption by Root 269 

Soil Roots, Water Roots, Air Roots 273 

§ 2. The Stem 282 

Buds 283 

Layers, Tillering 286 

Root-stocks 287 

Tubers 288 

Structure of the Stem 289 

Endogenous Plants 290 

Exogenous Plants 296 

Sieve-cells 303 

§ 3. Leaves 306 

Leaf Pores « 309 

Exhalation of Water Vapor 311 

Offices of Foliage 314 

Chap. IV.— Reproductive Organs 315 

§ 1. The Flower 316 

Fertilization 319 

Hybridizing 324 

Species. Varieties 326 

§ 2. Fruit 330 

Seed 332 

Embryo 333 

§ 3. Vitality of seeds and their influence on the Plants 

they produce 335 

Duration of Vitality 335 

Use of old and unripe seeds 338 

Density of seeds 339 

Absolute weight of seeds 340 

Signs of Excellence 345 

Ancestry. Race-vigor 346 

DIVISION III.— LIFE OF THE PLANT. 
Chap, l.— Germination 3ii> 

§ 1. Introductory 34!) 

§ 2. Phenomena of Germination 350 

§ 3. Conditions of Germination 351 

Proper Depth of Sowing 355 

§ 4. Chemical Physiology of Germination. 357 

Chemistry of Malt .' 358 

Chap. II. — 5 1. Food of the Plant when independent of the Seed 366 

§ 2. The Juices of the Plant. Their Nature and Movements369 

Flow of Sap 370 

Composition of Sap 376 

Kinds of Sap 378 

Motion of Nutrient Matters 379 

§ 3. Causes of Motion of the Juices 385 

Porosity of Tissues 385 

Imbibition 386 

Liquid Diffusion 390 

Osmose or Membrane Diffusion 393 

Root Action 399 

Selective Power of Plant 401 

§ 4. Mechanical effects of Osmose 406 

APPENDIX. 
Table.— Composition of Agricultural Products 409 



HOW CROPS GROW. 



INTRODUCTION. 



The object of agriculture is the production of certain 
plants and certain animals which are employed to feed, 
clothe and otherwise serve the human race. The first 
aim, in all cases, is the production of plants. 

Nature has made the most extensive provision for the 
spontaneous growth of an immense variety of vegetation ; 
but in those climates where civilization most certainly 
attains its fullest development, man is obliged to employ 
art to provide himself with the kinds and quantities of 
vegetable produce which his necessities or luxuries de- 
mand. In this defect, or, rather, neglect of nature, ag- 
riculture has its origin. 

The art of agriculture consists in certain practices and 
operations which have gradually grown out of an obser- 
vation and imitation of the best efforts of nature, or have 
been hit upon accidentally, or, finally, have been deduced 
from theory. 

The science of agriculture is the rational theory and 
systematic exposition of the successful art. 

Strictly considered, the art and science of agriculture 
are of equal age, and have grown together from the ear- 



2 HOW CROPS GROW. 

liest times. Those who first cultivated the soil by dig- 
ging, planting, manuring and irrigating, had their suffi- 
cient reason for every step. In all cases, thought goes 
before work, and the intelligent workman always has a 
theory upon which his practice is planned. ~No farm 
was ever conducted without physiology, chemistry, and 
physics, any more than an aqueduct or a railway was ever 
built without mathematics and mechanics. Every suc- 
cessful farmer is, to some extent, a scientific man. Let 
him throw away the knowledge of facts and the knowl- 
edge of principles which constitute his science, and he 
has lost the elements of his success. The farmer without 
his reasons, his theory, his science, can have no plan ; 
and these wanting, agriculture would be as complete a 
failure with him as it would be with a man of mere 
science, destitute of manual, financial and executive skill. 

Other qualifications being equal, the more advanced 
and complete the theory of which the farmer is the mas- 
ter, the more successful must be his farming. The more 
he knows, the more he can do. The more deeply, com- 
prehensively, and clearly he can think, the more econ- 
omically and advantageously can he work. 

That there is any opposition or conflict between science 
and art, between theory and practice, is a delusive error. 
They are, as they ever have been and ever must be, in the 
fullest harmony. If they appear to jar or stand in con- 
tradiction, it is because we have something false or incom- 
plete in what we call our science or our art ; or else we do 
not perceive correctly, but are misled by the narrowness 
and aberrations of our vision. It is often said of a ma- 
chine, that it was good in theory, but failed in practice. 
This is as untrue as untrue can be. If a machine has 
failed in practice, it is because it was imperfect in theory. 
It should be said of such a failure — the machine was 
good, judged by the best theory known to its inventor, 
but its incapacity to work demonstrates that the theory 
had a flaw. 



INTRODUCTION". 3 

But, although art and science are thus inseparable, it 
must not be forgotten that their growth is not altogether 
parallel. There are facts in art for which science can, as 
yet, furnish no adequate explanation. Art, though no 
older than science, grew at first more rapidly in vigor 
and in stature. Agriculture was practiced hundreds and 
thousands of years ago, with a success that does not com- 
pare unfavorably with ours. Nearly all the essential 
points of modern cultivation were regarded by the Ro- 
mans before the Christian era. The annals of the Chi- 
nese show that their wonderful skill and knowledge were 
in use at a vastly earlier date. 

So much of science as can be attained through man's 
unaided senses, reached considerable perfection early in 
the world's history. But that part of science which re- 
lates to things invisible to the unassisted eye, could not 
be developed until the telescope and the microscope had 
been invented, until the increasing experience of man and 
his improved art had created and made cheap the other 
inventions by whose aid the mind can penetrate the veil 
of nature. Art, guided at first by a very crude and im- 
perfectly-developed science, has, within a comparatively 
recent period, multiplied those instruments and means of 
research whereby science has expanded to her present 
proportions. 

The progress of agriculture is the joint work of theory 
and practice. In many departments great advances have 
been made during the last hundred years ; especially is 
this true in all that relates to implements and machines, 
and to the improvement of domestic animals. It is, 
however, in just these departments that an improved 
theory has had sway. More recent is the development of 
agriculture in its chemical and physiological aspects. In 
these directions the present century, or we might almost 
say the last fifty yeai*3, has seen more accomplished than 
all previous time. 



4 HOW CROPS GROW. 

The first book in the English language on the subjects 
which occupy a good part of the following pages, was 
written by a Scotch nobleman, the Earl of Dundonald, 
and was published at London in 1795. It is entitled: 
" A Treatise showing the Intimate Connection that sub- 
sists between Agriculture and Chemistry." The learned 
Earl, in his Introduction, remarked that "the slow pro- 
gress which agriculture has hitherto made as a science is 
to be ascribed to a want of education on the part of the 
cultivators of the soil, and the want of knowledge in such 
authors as have written on agriculture of the intimate 
connection that subsists between the science and that of 
chemistry. Indeed, there is no operation or process, not 
merely mechanical, that does not depend on chemistry, 
which is defined to be a knowledge of the properties of 
bodies, and of the effects resulting from their different 
combinations. " Earl Dundonald could not fail to see that 
chemistry was ere long to open a splendid future for the 
ancient art that always had been and always is to be the 
prime support of the nations. But when he wrote, how 
feeble was the light that chemistry could throw upon the 
fundamental questions of agricultural science ! The 
chemical nature of atmospheric air was then a discovery 
of barely twenty years' standing. The composition of 
water had been known but twelve years. The only ac- 
count of the composition of plants that Earl Dundonald 
could give was the following: '"Vegetables consist of 
mucilaginous matter, resinous matter, matter analogous 
to that of animals, and some proportion of oil. * * 
Besides these, vegetables contain earthy matters, formerly 
held in solution in the newly-taken-in juices of the 
growing vegetable." He further explains by mentioning 
on subsequent pages that starch belongs to the mucil- 
aginous matters, and that, on analysis by fire, vegetables 
yield soluble alkaline salts and insoluble phosphate of 
lime. But these salts, he held, were formed in the pro- 



INTRODUCTION. 5 

cess of burning, their lime excepted, and the fact of their 
being taken from the soil and constituting the indispen- 
sable food of plants, his Lordship was unacquainted with. 
The gist of agricultural chemistry with him was, that 
plants are "composed of gases with a small proportion of 
calcareous matter;" for "although this discovery may 
appear to be of small moment to the practical farmer, yet 
it is well deserving of his attention and notice, as it 
throws great light on the nature and food of vegetables." 
The fact being then known that plants absorb carbonic 
acid from the air, and employ its carbon in their growth, 
the theory was held that fertilizers operate by promoting 
the conversion of the organic matter of the soil or of 
composts into gases, or into soluble humus, which were 
considered to be the food of plants. 

The first accurate analysis of a vegetable substance was 
not accomplished until fifteen years after the publication 
of Dundonald's Treatise, and another like period passed 
before the means of rapidly multiplying good analyses 
had been worked out by Liebig. So late as 1838, the Got- 
tingen Academy offered a prize for a satisfactory solution 
of the then vexed question whether the ingredients of 
ashes are essential to vegetable growth. It is, in fact, 
during the last fifty years that agricultural chemistry has 
come to rest on sure foundations. Our knowledge of the 
structure and physiology of plants is of like recent devel- 
opment. What immense practical benefit the farmer has 
gathered from this advance of science ! Chemistry has 
ascertained what vegetation absolutely demands for its 
growth, and points out a multitude of sources whence 
the requisite materials for crops can be derived. Cato 
and Columella knew indeed that ashes, bones, bird- 
dung and green manuring, as well as drainage and aera- 
tion of the soil, were good for crops ; but that carbonic 
acid, potash, phosphate of lime, and compounds of nitro- 
gen are the chief pabulum of vegetation, they did not 



G HOW CROPS GROW. 

know. They did not know that the atmosphere dissolves 
the rocks, and converts inert stone into nutritive soil. 
These grand principles, understood in many of their de- 
tails, are an inestimable boon to agriculture, and intelli- 
gent farmers have not been slow to apply them in prac- 
tice. The vast trade in phosphatic and Peruvian gnano, 
and in nitrate of soda ; the great manufactures of oil of 
vitriol, of superphosphate of lime, of fish fertilizers ; and 
the mining of fossil bones and of potash salts, are indus- 
tries largely or entirely based upon and controlled by 
chemistry in the service of agriculture. 

Every day is now the witness of new advances. The 
means of investigation, which, in the hands of the scien- 
tific experimenter, have created within the writer's mem- 
ory such arts as photography and electro-metallurgy, and 
have produced the steam-engine, the telegraph, the tele- 
phone and the electric light, are working and shall ever- 
more continue to work progress in the art of agriculture. 
This improvement will not consist so much in any re- 
markable discoveries that shall enable us to ' * grow two 
blades of grass where but one grew before;" but in the 
gradual disclosure of the reasons of that which we have 
long known, or believed we knew ; in the clear separa- 
tion of the true from the seemingly true, and in the ex- 
change of a wearying uncertainty for settled and positive 
knowledge. 

It is the boast of some who affect to glory in the suf- 
ficiency of practice and decry theory, that the former is 
based upon experience, which is the only safe guide. But 
this is a one-sided view of the matter. Theory is also 
based upon experience, if it be worth the name. The 
fancies of an ignorant and undisciplined mind are not 
theory as that term is properly understood. Theory, in 
the strict scientific sense, is always a deduction from 
facts, and the best deduction of which the stock of facts 
in our possession admits. It is therefore also the inter- 



INTRODUCTION. 7 

pretation of facts. It is the expression of the ideas which 
facts awaken when submitted to a fertile imagination and 
well-balanced judgment. A scientific theory is intended 
for the nearest possible approach to the truth. Theory 
is confessedly imperfect, because our knowledge of facts 
is incomplete, our mental insight weak, and our judg- 
ment fallible. But the scientific theory which is framed 
by the contributions of a multitude of earnest thinkers 
and workers, among whom are likely to be the most gifted 
intellects and most skillful hands, is, in these days, to a 
great extent worthy of the Divine truth in nature, of 
which it is the completest human conception and ex- 
pression. 

Science employs, in effecting its progress, essentially 
the same methods that are used by merely practical men. 
Its success is commonly more rapid and brilliant, because 
its instruments of observation are finer and more skill- 
fully handled ; because it experiments more industriously 
and variedly, thus commanding a w T ider and more fruit- 
ful experience ; because it usually brings a more culti- 
vated imagination and a more disciplined judgment to 
bear upon its work. The devotion of a life to discovery 
or invention is sure to yield greater results than a desul- 
tory application made in the intervals of other absorbing 
pursuits. It is then for the iuterest of the farmer to 
avail himself of the labors of the man of science, when 
the latter is willing to inform himself in the details of 
practice, so as rightly to comprehend the questions which 
press for a solution. 

Agricultural science, in its widest scope, comprehends 
a vast range of subjects. It includes something from 
nearly every department of human learning. The natu- 
ral sciences of geology, meteorology, mechanics, physics, 
chemistry, botany, zoology and physiology, are most in- 
timately related to it. It is not less concerned with so- 
cial and political economy. In this treatise it will not be 



8 HOW CROPS GROW. 

attempted to touch, much less cover, all this ground, but 
some account will be given of certain subjects whose un- 
derstanding will be of the most direct service to the agri- 
culturist. The Theory of Agriculture, as founded on 
chemical, physical and physiological science, in so far as 
it relates to the Chemical Composition, the Structure and 
the Life of the Plant, is the topic of this volume. 

Some preliminary propositions and definitions may be 
serviceable to the reader. 

Science deals with Matter and Force. 

Matter is that which has weight and bulk. 

Force is the cause of changes in matter — it is appre- 
ciable only by its effects upon matter. 

Force resides in and is inseparable from matter. 

Force manifests itself in motion and change. 

All matter is perpetually animated by force — is there- 
fore never at rest. What we call rest in matter is simply 
motion too fine for our perceptions. 

The different kinds of matter known to science have 
been resolved into some seventy chemical elements or sim- 
ple substances. 

The elements of chemistry are forms of matter which 
have thus far resisted all attempts at their simplification 
or decomposition. 

In ordinary life we commonly encounter but twelve 
kinds of matter in their elementary state, viz. : 



Oxygen, 


Carbon, 


Mercury, 


Tin, 


Nitrogen, 


Iron, 


Copper, 


Silver, 


Sulphur, 


Zinc, 


Lead, 


Gold. 



The numberless other substances with which we are 
familiar, are mostly compounds of the above, or of twelve 
other elements, viz. : 



Hydrogen, 


Silicon, 


Calcium, 


Manganese, 


Phosphorus, 


Potassium. 


Magnesium, 


Chromium, 


Chlorine, 


Sodium, 


Aluminum, 


Nickel. 



INTRODUCTION. 



So far as human agency goes, these chemical elements 
are indestructible as to quantity, and not convertible 
one into another. 

We distinguish various natural manifestations of force 
which, acting on or through matter, produce all material 
phenomena. In the subjoined scheme the recognized 
forces are to some extent classified and defined, in a man- 
ner that may prove useful to the reader. 



Act at sensi- 
ble and in- 
sensible 
distances 



Act only at 
insensible 
distances 



Repulsive 
Attractive 

and 
Repulsive 



Attractive 



LIGHT 
HEAT 

ELECTRICITY 
Magnetism 

r GRAVITATION 

COHESION 

Crystallization 

ADHESION 

Solution 

Osmose 
[AFFINITY 

VITALITY 



J Radiant 

> Inductive 
Cosmical 

Molecular 

Atomic 
Organic 



►Physical 



Chemical 
Biological 



Within human experience the different kinds of force 
are mostly convertible each into the others, and must 
therefore be regarded as fundamentally one and the same. 
Force, like matter, is indestructible. Force acting on 
a body may either increase its Kinetic Energy, or be 
stored up in it as Potential Energy. Kinetic (or ac- 
tual) energy is the energy of a moving body. Potential 
(or possible) energy is the energy which a body may be 
able to exert because of its state or position. A falling 
stone or running clock gives out actual energy. The 
stone while being raised, or the clock while winding, ac- 
quires and stores potential energy. In a similar manner 
kinetic solar energy, reaching the earth as light, heat and 
chemical force, not only sets in operation the visible ac- 
tivities of plants, but accumulates in them a store of po- 
tential energy which, when they serve as food or fuel, re- 
appears as kinetic energy in the forms of animal heat, 
muscular and nervous activity, or as fire and light. 

The sciences that more immediately relate to agricult- 
ure are Physics, Chemistry and Biology. 



10 HOW CROPS GROW. 

Physics, or "natural philosophy," is the science 
which considers the general properties of matter and such 
phenomena as are not accompanied by essential change 
in its obvious qualities. All the forces in the preceding 
scheme, save the last two, manifest themselves through 
matter without destroying or masking the matter itself. 
Iron may be hot, luminous, or magnetic, may fall to the 
ground, be melted, welded, and crystallized ; but it re- 
mains iron, and is at once recognized as such. The forces 
whose play does not disturb the evident characters of sub- 
stances are physical. 

Chemistry is the science which studies the proper- 
ties peculiar to the various kinds of matter, and those 
phenomena which are accompanied by a fundamental 
change in the matter acted on. Iron rusts, wood burns, 
and both lose all the external characters that serve for 
their identification. They are, in fact, converted into 
other substances. Chemical attraction, affinity, or chem- 
ism, as it is variously termed, unites two or more ele- 
ments into compounds, unites compounds together into 
more complex compounds ; and, under the influence of 
heat, light, and other agencies, is annulled or overcome, 
so that -compounds resolve themselves into simpler com- 
binations or into their elements. Chemistry is the science 
of composition and decomposition ; it considers the laws 
and results of affinity. 

BicUogy, or physiology, unfolds the laws of the 
propagation, development, sustenance, and death of liv- 
ing organisms, both plants and animals. 

When we assert that the object of agriculture is to de- 
velop from the soil the greatest possible amount of cer- 
tain kinds of vegetable and animal produce at the least 
cost, we suggest the topics which are most important for 
the agriculturist to understand. 

The farmer deals with the plant, with the soil, with 
manures. These stand in close relation to each other, 



INTRODUCTION. 11 

and to the atmosphere which constantly surrounds and 
acts upon them. How the plant grows, — the conditions 
under which it flourishes or suffers detriment, — the ma- 
terials of which it is made, — the mode of its construction 
and organization, — how it feeds upon the soil and air, — : 
how it serves as food to animals, — how the air, soil, 
plant, and animal stand related to each other in a per- 
petual round of the most beautiful and wonderful trans- 
formations, — these are some of the grand questions that 
come before us ; and they are. not less interesting to the 
philosopher or man of culture, than important to the 
farmer who depends upon their practical solution for his 
comfort ; or to the statesman, who regards them in their 
bearings upon the weightiest of political considerations. 



DIVISION 1. 

CHEMICAL COMPOSITION OF THE PLANT. 

CHAPTER 1. 

THE VOLATILE PART OF PLANTS. 

§ L 

DISTINCTIONS AND DEFINITIONS. 

Organic and Inorganic Matter. —All matter may 
be divided into two great classes — Organic and Inorganic. 

Organic matter is the product of growth, or of vital 
organization, whether vegetable or animal. It is mostly 
combustible, i. e., it may be easily set on fire, and burns 
away into invisible gases. Organic matter either itself 
constitutes the organs of life and growth, and has a pecu- 
liarly organized structure, inimitable by art, — is made up 
of cells, tubes or fibres (wood and flesh) ; or else is a 
mere result or product of the vital processes, and desti- 
tute of this structure (sugar and fat). 

All matter which is not a part or product of a living 
organism is inorganic or mineral matter (rocks, soils, 
water, and air). Most of the naturally-occurring forms 
of inorganic matter which directly concern agricultural 
chemistry are incombustible, and destitute of anything 
like organic structure. 

By the processes of combustion and decay, organic 
matter is disorganized or converted into inorganic matter, 
while, on the contrary, by vegetable growth inorganic 
matter is organized, and becomes organic. 
13 



1-4 HOW CROPS GROW. 

Organic matters are in general characterized by com- 
plexity of constitution, and are exceedingly numerous 
and various ; while inorganic bodies are of simpler com- 
position, and comparatively few in number. 

Volatile and Fixed Matter. — All plants and ani- 
mals, taken as a whole, and all of their organs, consist of 
a volatile and fixed part, which may be separated by 
burning ; the former — usually by far the larger share — 
passing into and mingling with the air as invisible gases ; 
the latter — forming, in general, but from one to five per 
cent, of the whole — remaining as ashes. 

Experiment 1.— A splinter of wood heated in the flame of a lamp 
takes fire, burns, and yields volatile matter, which consumes with flame, 
and ashes, which are the only visible residue of the combustion. 

Many organic bodies, products of life, but not essential 
vital organs, as sugar, citric acid, etc., are completely 
volatile when in a state of purity, and leave no ash. 

Use of the Terms Organic and Inorganic. — It is 
usual among agricultural writers to confine the term or- 
ganic to the volatile or destructible portion of vegetable 
and animal bodies, and to designate their ash-ingredients 
as inorganic matter. This is not an entirely accurate 
distinction. What is found in the ashes of a tree or of a 
seed, in so far as it was an essential part of the organism, 
was as truly organic as the volatile portion, and, by sub- 
mitting organic bodies to fire, they may be entirely con- 
verted into inorganic matter, the volatile as well as the 
fixed parts. 

Ultimate Elements that Constitute the Plant. — 
Chemistry has demonstrated that the volatile and de- 
structible part of organic bodies is chiefly made up of four 
substances, viz. : carbon, oxygen, hydrogen, and nitrogen, 
and contains two other elements in lesser quantity, viz. : 
sulphur and phosphorus. In the ash we may find phos- 
phorus, sulphur, silicon, chlorine, potassium, sodium, cal- 



THE VOLATILE PART OF PLANTS. 15 

cium, magnesium, iron, and manganese, as well as oxy- 
gen, carbon, and nitrogen.* 

These fourteen bodies are elements, which means, in 
chemical language, that they cannot be resolved into 
other substances. All the varieties of vegetable and ani- 
mal matter are compounds, — are composed of and may be 
resolved into these elements. 

The above-named elements being essential to the or- 
ganism of every plant and animal, it is of the highest im- 
portance to make a minute study of their properties. 



§ 2. 



ELEMENTS OF THE VOLATILE PART OF PLANTS. 

For the sake of convenience we shall first consider the 
elements which constitute the combustible part of plants, 
viz. : 

Carbon, Nitrogen, Sulphur, 

Oxygen, Hydrogen, Phosphorus. 

The elements which belong exclusively to the ash will 
be noticed in a subsequent chapter. 

Carbon, in the free state, is a solid. We are familiar 
with it in several forms, as lamp-black, charcoal, black- 
lead, and diamond. Notwithstanding the substances 
just named present great diversities of appearance and 
physical characters, they are identical in a certain chem- 
ical sense, as by burning they all yield the same product, 
viz. : carbonic acid gas, also called carbon dioxide. 

That carbon constitutes a large part of plants is evi- 
dent from the fact that it remains in a tolerably pure 
state after the incomplete burning of wood, as is illus- 
trated in the preparation of charcoal. 



* Rarely, or to a slight extent, lithium, rubidium, iodine, bromine, 
fluorine, barium, copper, zinc, titanium, and boron. - 



16 HOW CROPS GROW. 

Exp. 2.— If a splinter of dry pine wood be set on fire and the burning 
end be gradually passed into the mouth of a narrow tube (see figure 1), 
whereby the supply of air is cut off, or if it be thrust into 
sand, the burning is incomplete, and a stick of charcoal re- 
mains. 

Carbonization and Charring are terms used to 
express the blacken ir,g of organic bodies by heat, 
and are due to the separation of carbon in the free 
or uncombined state. 

The presence of carbon in animal matters also is 
shown by subjecting them to incomplete com- 
bustion. 

Exp. 3. — Hold a knife-blade in the flame of a tallow candle ; 
the full access of air is thus prevented, — a portion of carbon „. .. 
escapes combustion, and is deposited on the blade in the form *' 
of lamp-black. 

Oil of turpentine and petroleum (kerosene) contain so 
much carbon that a portion ordinarily escapes in the free 
state as smoke, when they are set on fire. 

When bones are strongly heated in closely-covered iron 
pots, until they cease yielding any vapors, there remains 
in the vessels a mixture of impure carbon with the earthy 
matter (phosphate of lime) of the bones, which is largely 
used in the arts, chiefly for refining sugar, but also in the 
manufacture of fertilizers under the name of animal char- 
coal, or bone-black. 

Lignite, bituminous coal, antliracite, coke — the porous, 
hard, and lustrous mass left when bituminous coal is 
heated with a limited access of air, and the metallic ap- 
pearing gas-carbon that is found lining the iron cylinders 
in which illuminating coal-gas is prepared, all consist 
largely or chiefly of carbon. They usually contain more 
or less incombustible matters, as well as a little oxygen, 
hydrogen, nitrogen, and sulphur. 

The different forms of carbon possess a greater or less 
degree of porosity and hardness, according to their origin 
and the temperature at which they are prepared. 

Carbon, in most of its forms, is extremely indestructi- 



THE VOLATILE PART OF PLANTS. 17 

ble under ordinary circumstances. Hence stakes and 
fence posts, if charred before setting in the ground, last 
much longer than when this treatment is neglected. 

The porous varieties of carbon, especially wood char- 
coal and bone-black, have a remarkable power of absorb- 
ing gases and coloring matters, which is taken advantage 
of in the refining of sugar. They also destroy noisome 
odors, and are used for purposes of disinfection. 

Carbon is the characteristic ingredient of all organic 
compounds. There is no single substance that is the ex- 
clusive result of vital organization, no ingredient of the 
animal or vegetable produced by their growth, that does 
not contain this element. 

Oxygen. — Carbon is a solid, and is recognized by our 
senses of sight and feeling. Oxygen, on the other hand, 
is an air or gas, invisible, odorless, tasteless, and not dis- 
tinguishable in any way from ordinary air by the unas- 
sisted senses. 

It exists in the free (uncombined) state in the atmos- 
phere we breathe, but there is no means of obtaining it 
pure except from some of its compounds. Many metals 
unite readily with oxygen, forming compounds (oxides) 
which by heat separate again into their ingredients, and 
thus furnish the means of procuring pure oxygen. Iron 
and copper, when strongly heated and exposed to the air, 
acquire oxygen, but from the oxides of these metals 
(forge cinder, copper scale) it is not possible to separate 
pure oxygen. If, however, the metal mercury (quicksil- 
ver) be kept for a long time near the temperature at 
which it boils, it is slowly converted in(o a red powder 
(red precipitate, red oxide of mercury, or mercuric ox- 
ide), which on being more strongly heated is decomposed, 
yielding metallic mercury and gaseous oxygen in a pure 
state. 

The substance usually employed as the most convenient 
source of oxygen gas is the white salt called potassium 
2 



18 



HOW CROPS GROW. 



chlorate. Exposed to heat, this body melts, and present- 
ly evolves oxygen in great abundance. 

Exp. 4.— The following figure illustrates the apparatus employed for 
preparing and collecting this gas. 

A tube of difficultly fusible glass, 8 inches long and % inch wide, con- 
tains the red oxide of mercury or potassium chlorate.* To its mouth is 
connected, air-tight, by a cork, a narrow tube, the free extremity of 
which passes under the shelf of a tub nearly filled with water. The 
shelf has, beneath, a funnel-shaped cavity opening above by a narrow 
orifice, over which a bottle filled with water is inverted. Heat being 




Fig. 2. 



applied to the wide tube, the common air it contains is first expelled, 
and presently, oxygen bubbles rapidly into the bottle and displaces 
the water. When the bottle is full, it may be corked and set aside, and 
its place supplied by another. Fill four pint bottles with the gas, and 
set them aside with their mouths in tumblers of water. From one 
ounce of potassium chlorate about a gallon of oxygen gas may be thus 
obtained, which is not quite pure at first, but becomes nearly so on 
standing over water for some hours. When the escape of gas becomes 
slow and cannot be quickened by increased heat, remove the delivery- 
tube from the water, to prevent the latter receding and breaking the' 
apparatus. 

As this gas makes no peculiar impressions on the senses, 



* The potassium chlorate is best mixed with about one-quarter its 
weight of powdered black oxide of manganese, as this facilitates the 
preparation, and renders the heat of a common alcohol lamp sufficient. 



THE VOLATILE PART OF PLANTS. 19 

we employ its behavior toward other bodies for its recog- 
nition. 

Exp. 5.— Place a burning splinter of -wood in a vessel of oxygen (lifted 
for that purpose, mouth upward, from the water). The flame is at once 
greatly increased in brilliancy. Now remove the splinter from the 
bottle, blow out the flame, and thrust the still glowing point into the 
oxygen. It is instantly relighted. The experiment may be repeated 
many times. This is the usual test for oxygen gas. 

Combustion. — When the chemical union of two bodies 
takes place with such energy as to produce visible phe- 
nomena of fire or flame, the process is called combustion. 
Bodies that burn are combustibles, and the gas in which 
a substance burns is called a supporter of combustion. 

Oxygen is the grand supporter of combustion, and 
nearly all cases of burning met with in ordinary experi- 
ence are instances of chemical union between the oxygen 
of the atmosphere and some other body or bodies. 

The rapidity or intensity of combustion depends upon 
the quantities of oxygen and of the combustible that 
unite within a' given time. Forcing a stream of air into 
a fire increases the supply of oxygen and excites a more 
vigorous combustion, whether it be done by a bellows or 
result from ordinary draught. 

Oxygen exists in our atmosphere to the extent of about 
one-fifth of the bulk of the latter. When a burning body 
is brought into unmixed oxygen, its combustion is, of 
course, more rapid than in ordinary air, four-fifths of 
which is a gas, presently to be noticed, that is compara- 
tively indifferent in its chemical affinities toward most 
bodies. 

In the air a piece of bitming charcoal soon goes out ; 
but if plunged into oxygen, it burns with great rapidity 
and brilliancy. 

Exp. 6.— Attach a slender bit of charcoal to one end of a sharpened 
wire that is passed through a wide cork or card ; heat the charcoal to 
redness in the flame of a lamp, and then insert it into a bottle of oxy- 
gen, Fig. 3. When the combustion has declined, a suitable test applied 



20 



HOW CROPS GROW. 



to the air of the bottle will demonstrate that another invisible gas has 
taken the place of the oxygen. Such a test is lime-water.* 
On pouring some of this into the bottle and agitating 
vigorously, the previously clear liquid becomes milky, 
and, on standing, a white deposit, or precipitate, as the 
chemist terms it, gathers at the bottom of the vessel. 
Carbon, by thus uniting to oxygen, yields carbonic acid 
gas, which in its turn combines with lime, producing 
carbonate of lime. These substances will be further 
noticed in a subsequent chapter. 




Metallic iron is incombustible in the at- 
mosphere undexordinary circumstances, but 
if heated to reariess and brought into pure 
oxygen gas, it burns as readily as wood burns in the air. 



Fig. 3. 




Exp. 7.— Provide a thin knitting-needle, heat one end red hot, and 
sharpen it by means of a file. Thrust the point thus 
made into a splinter of wood (a bit of the stick of a 
match, \ inch long); pass the other end of the needle 
through a wide, flat cork for a support ; set the wood on 
fire, and immerse the needle in a bottle of oxygen, Fig. 
4. Alter the wood consumes, the iron itself takes fire 
and burns with vivid scintillations. It is converted into 
two distinct oxides of iron, of which one,— ferric oxide, — 
will be found as a yellowish-red coating on the sides of 
the bottle ; the other,— magnetic oxide,— will fuse to 
black, brittle globules, which falling, often melt quite 
into the glass. 

The only essential difference between these and ordi- 
nary cases of combustion is the intensity with which the 
process goes on, due to the more rapid access of oxygen 
to the combustible. 

Many bodies unite slowly with oxygen, — oxidize, as it 
is termed, — without these phenomena of light and intense 
heat which accompany combustion. Thus iron rusts, lead 
tarnishes, wood decays. All these processes are cases of 
oxidation, and cannot go on in the absence of oxygen. 

Since the action of oxygen on wood and other organic 
matters at common temperatures appears to be analogous 

* To prepare lime-water, put a piece of unslaked lime, as large as a 
chestnut, into a pint of water, and after it has fallen to powder, agitate 
the whole for a few minutes in a well-stoppered bottle. On standing, 
the exeess of lime will settle, and the perfectly clear liquid above it is 
ready for use. 



THE VOLATILE PART OF PLANTS. 21 

in a chemical sense to actual burning, Liebig has pro- 
posed the term eremacausis (slow burning), to designate 
the chemical process of oxidation which takes place in 
decay, and which is concerned in many transformations, 
as in the making of vinegar and the formation of salt- 
peter.* 

Oxygen is necessary to organic life. The act of breath- 
ing introduces it into the lungs and blood of animals, 
where it aids the important office of respiration. Ani- 
mals, and plants as well, speedily perish if deprived of 
free oxygen, which has therefore been called vital air. 

Oxygen has a nearly universal tendency to combine 
with other substances, and form with them new com- 
pounds. With carbon, as we have seen, it forms carbonic 
acid gas or carbon dioxide. With iron it unites in vari- 
ous proportions, giving origin to several distinct oxides. 
In decay, putrefaction, fermentation, and respiration, 
numberless new products are formed, the results of its 
chemical affinities. 

Oxygen is estimated to be the most abundant body in 
nature. In the free state, but mixed with other gases, it 
constitutes one-fifth of the bulk of the atmosphere. In 
chemical union with other bodies, it forms eight-ninths 
of the weight of all the water of the globe, and one-third 
of its solid crust, — its soils and rocks, — as well as of all 
the plants and animals which exist upon it. In fact, 
there are but few compound substances occurring in or- 
dinary experience into which oxygen does not enter as a 
necessary ingredient. 

Nitrogen. — This body is the other chief constituent of 
the atmosphere, of which it makes up about four-fifths 
the bulk, and in which its office would appear to be 

* Recent investigation has demonstrated that the oxidations which 
Liebig classed under the term eremacausis, are for the most part strict- 
ly dependent on the vital processes of extremely minute organisms, 
which are in general characterized by the terms microbes or micro- 
demes, and are more specifically designated bacteria, i. e., "rod-shaped 
animalcules or plantleis." 



22 HOW CROPS GROW. 

mainly that of diluting and tempering the affinities of 
oxygen. Indirectly, however, it serves other most im- 
portant uses, as will presently be seen. 

For the preparation of nitrogen we have only to remove 
the oxygen from a portion of atmospheric air. This may 
be accomplished more or less perfectly by a variety of 
methods. We have just learned that the process of burn- 
ing is a chemical union of oxygen with the combustible. 
If, now, we can find a body which is very combustible 
and one- which at the same time yields by union with ox- 
ygen a product that may be readily removed from the air 
in which it is formed, the preparation of nitrogen from 
ordinary air becomes easy. Such a body is phosphorus, 
a substance to be noticed in some detail presently. 

Exp. 8.— The bottom of a dinner-plate is covered half an inch deep 
with water ; a bit of chalk hollowed out into a little cup is floated on 
the water by means of a large flat cork or a piece of wood ; into this 
cup a morsel of dry phosphorus as large as a pepper- 
corn is placed, which is then set on fire and covered by 
a capaciovis glass bottle or bell-jar. The phosphorus 
burns at first with a vivid light, which is presently ob- 
scured by a cloud of snow-like phosphoric acid. The 
combustion goes on, however, until nearly all the oxy- 
gen is removed from the included air. The air is at 
first expanded by the heat of the flame, and a portion 
of it escapes from the vessel ; afterward it diminishes 
in volume as its oxygen is removed, so that it is need- jij ^ 

ful to pour water on the plate to prevent the external 
air from passing into the vessel. After some time the white fume will 
entirely fall, and be absorbed by the water, leaving the inclosed nitro- 
gen quite clear. 

Exp. 9.— Another instructive method of preparing nitrogen is the fol- 
lowing : A handful of green vitriol (protosulphate of iron or ferrous 
sulphate) is dissolved in half a pint of water, the solution is put into 
a quart bottle, a gill of ammonia-water or fresh potash-lye is added, 
the bottle stoppered, and the mixture vigorously agitated for some 
minutes ; the stopper is then lifted, to allow fresh air to enter, and the 
whole is again agitated as before. This is repeated occasionally for half 
an hour or more, until no further absorption takes place, when nearly 
pure nitrogen remains in the bottle. 

Free nitrogen, under ordinary circumstances, mani- 
fests no active properties, but is best characterized by its 
chemical indifference to most other bodies. That it is 




THE VOLATILE PART OF PLANTS. 23 

incapable of supporting combustion is proved by the first 
method we have instanced for its preparation. 

Exp. 10.— A burning splinter is immersed in the bottle containing the 
nitrogen prepared by the second method, Exp. 9 ; the flame immediate- 
ly goes out. 

Nitrogen cannot maintain respiration, so that animals 
perish if confined in it. Vegetation also dies in an at- 
mosphere of this gas. For this reason it was formerly 
called Azote (against life). In general it is difficult to 
effect direct union of nitrogen with other bodies, but at 
a high temperature, in presence of alkalies, it unites with 
carbon, forming cyanides. 

The atmosphere is the great store and source of nitro- 
gen in nature. In the mineral kingdom, especially in 
soils, it occurs in small relative proportion, but in large 
aggregate quantity as an ingredient of saltpeter and other 
nitrates, and of ammonia. It is a constant constituent 
of all plants, and in the animal it is a never-absent com- 
ponent of the working tissues, the muscles, tendons and 
nerves, and is hence an indispensable ingredient of food. 

Hydrogen. — Water, which is so abundant in nature, 
and so essential to organic existence, is a compound of 
two elements, viz. : oxygen, that has already been consid- 
ered, and hydrogen, which we now come to notice. 

Hydrogen, like oxygen, is a gas, destitute, when pure, 
of either odor, taste, or color. It does not occur nat- 
urally in the free state, except in small quantity in the 
emanations from boiling springs and volcanoes. Its most 
simple preparation consists in abstracting oxygen from 
water by means of agents which have no special affinity 
for hydrogen, and therefore leave it uncombined. 

Sodium, a metal familiar to the chemist, has such an 
attraction for oxygen that it decomposes water with great 
rapidity. 

Exp. 11.— Hydrogen is therefore readily procured by inverting a bot- 
tle full of water in a bowl, and inserting into it a bit of sodium as large 
as a pea. The sodium should first be wiped free from the naphtha in 



24 



HOW CHOPS GROW. 



which it is kept, and then be wrapped tightly in several folds of paper. 
On bringing it, thus prepared', under the mouth of the bottle, it floats 
upward, and when the water penetrates the paper, an abundant escape 
of gas occurs. 

Metallic iron, when at a red heat, rapidly decomposes 
water, uniting with oxygen and setting hydrogen free, 
as may be shown by passing steam from boiling water 
through a gun-barrel filled with iron-turnings and heated 
to bright redness. Certain acids which contain hydro- 
gen are decomposed by iron, zinc, and some other metals, 
their hydrogen heing separated as gas, while the metal 
takes the place of the hydrogen with formation of a salt. 
Hydrochloric acid (formerly called muriatic acid) is a 
compound of hydrogen with chlorine, and may accord- 
ingly be termed hydroge?i chloride. When this acid is 
poured upon zinc the latter takes the chlorine, forming 
zinc chloride, and hydrogen escapes as gas. Chemists 
represent such changes by the use of symbols (first letters 
of the names of chemical elements), as follows : 

gg + Zn=Zng + gor 
2 (H CI) + Zn = Zn Cl 2 -f H, 

Exp. 12.— Into a bottle fitted with cork, funnel, and delivery tubes (Fig. 
6) an ounce of iron tacks or zinc 
clippings is introduced, a gill 
of water is poured upon them, 
and lastly an ounce of hydro- 
chloric acid is added. A brisk 
effervescence shortly com- 
mences, owing to the escape 
of nearly pure hydrogen gas, 
which may be collected in a 
bottle filled with water as di- 
rected for oxygen. The first 
portions that pass over are 
mixed with air, and should be 
rejected, as the mixture is dan- 
gerously explosive. 

One of the most strik- 
ing properties of free hy- Fig. 6. 
drogen is its levity. It is the lightest body in nature 




THE VOLATILE PART OF PLANTS. 



25 



that 




lias been weighed, being fourteen and a half times 
lighter than common air. It is hence 
|iised in filling balloon s. Another property 
is its combustibility ; it inflames on contact 
with a lighted taper, and burns with a 
flame that is intensely hot, though scarcely 
luminous if the gas be pure. Finally, it 
is itself incapable of supporting the com- 
ics- 7 - bustion of a taper. 

Exp. 13.— All these characters may be shown by the following single 
experiment. A bottle full of hydrogen is lifted from the water over 
which it has been collected, and a taper attached to a bent wire, Fig. 7, 
is brought to its mouth. At first a slight explosion is heard from the 
sudden burning of a mixture of the gas with air that forms at the mouth 
of the vessel; then the gas is seen burning on its lower surface with a 
pale flame. If now the taper be passed into the bottle it will be extin- 
guished; on lowering it again, it will be relighted by the burning gas; 
finally, if the bottle be suddenly turned mouth upwards, the light hy- 
drogen rises in a sheet of flame. 

In the above experiment, the hydrogen burns only 
where it is in contact with atmospheric oxygen ; the pro- 
duct of the combustion is an oxide of hydrogen, the uni- 
versally diffused compound, water. The conditions 'of 
the last experiment do not permit the collection or iden- 
tification of this water ; its production can, however, 
readily be demonstrated. 

Exp. 14.— The arrangement shown in Fig. 8 may be employed to exhibit 




IliiMMIllIIi™^ 



Fig. & 



the formation of water by the burning of hydrogen. Hydrogen gas is 
generated from zinc and dilute acid in the two-necked bottle. Thus 



26 HOW CROPS GROW. 

produced, it is mingled with spray, to remove which it is made to 
stream through a tube loosely tilled with cotton. After air has been 
entirely displaced from the apparatus, the gas is ignited at the up- 
curved end of the narrow tube, and a clean bell-glass is supported over 
the flame. Water collects at once, as dew, on the interior of the bell, 
and shortly flows down in drops into a vessel placed beneath. 

In the mineral world we scarcely find hydrogen occur- 
ring in much quantity, save as water. It is a constant 
ingredient of plants and auimals, and of nearly all the 
numberless substances which are products of organic life. 

Hydrogen forms with carbon a large number of com- 
pounds, the most common of which are the volatile oils, 
like oil of turpentine, oil of lemon, etc. The chief illu- 
minating ingredient of coal gas (ethylene or olefiant gas), 
the coal or rock oils (kerosene), together with benzine 
and paraffine, are so-called hydro-carbons. 

Sulphur is a well-known solid substance, occurring in 
commerce either in sticks (brimstone, roll sulpliur) or as 
a fine powder (flowers of sulphur), having a pale yellow 
color, and a peculiar odor and taste. 

.Uncombined sulphur is comparatively rare, the com- 
mercial supplies being almost exclusively of volcanic ori- 
gin ; but, in one or other form of combination, this ele- 
ment is universally diffused. 

Sulphur is combustible. It burns in the air with a 
pale blue flame, in oxygen gas with a beautiful purple- 
blue flame, yielding in both cases a suffocating and fum- 
ing gas of peculiar nauseous taste, which is called sul- 
phurous acid gas or sulphur dioxide. 

Exp. 15.— Heat a bit of sulphur as large as a grain of wheat on a slip 
of iron or glass, over the flame of a spirit lamp, for observing its fusion, 
combustion, and the development of sulphur dioxide. Further, scoop 
out a little hollow in a piece of chalk, twist a wire round the latter to 
serve for a handle, as in Fig. 3; heat the chalk with a fragment of sul- 
phur upon it until the latter ignites, and bring it into a bottle of oxygen 
gas. The purple flame is shortly obscured by an opaque white fume of 
sulphur dioxide. 

Sulphur forms with oxygen another compound, the tri- 
oxide, which, in combination with water, constitutes com- 



THE VOLATILE PART OF PLANTS. 27 

mon sulphuric acid, or oil of vitriol. This oxide is devel- 
oped to a slight extent during the combustion of sulphur 
in the air and the acid is prepared on a large scale for 
commerce by a complicated process. 

Sulphur unites with most of the metals, yielding com- 
pounds known as sulphides, or formerly as sulphur ets. 
These exist in nature in large quantities, especially the 
sulphides of iron, copper, and lead, and many of them 
are valuable ores. Sulphides may be formed artificially 
by heating most of the metals with sulphur. 

Exp. 16.— Heat the bowl of a tobacco-pipe to a low red heat in a stove 
or furnace ; have in readiness a thin iron wire or watch-spring made 
into a spiral coil ; throw into the pipe-bowl some lumps of sulphur, and 
when these melt and boil, with formation of a red vapor or gas, intro- 
duce the iron coil, previously heated to redness, into the sulphur vapor. 
The sulphur and iron unite; the iron, in fact, burns in the sulphur gas, 
giving rise to a black iron sulphide, in the same manner as in Exp. 7 it 
burned in oxygen gas and produced an iron oxide. The iron sulphide 
melts to brittle, round globules, and remains in the pipe-bowl. 

With hydrogen, the element we are now considering 
unites to form a gas that possesses in a high degree the 
odor cf rotten eggs, and is, in fact, the chief cause of the 
noisomeness of this kind of putridity. This gas, com- 
monly called sulphuretted hydrogen, or hydrogen sulphide, 
is dissolved in, and evolved abundantly from, the water 
of sulphur springs. It may be produced artificially by 
acting on some metallic sulphides with dilute sulphuric 
or hydrochloric acid. 

Exp. 17.— Place a lump of the iron sulphide prepared in Exp. 16 in a cup 
or wine-glass, add a little water, and lastly a little hydrochloric acid. 
Bubbles of hydrogen sulphide will shortly escape. 

In soils, sulphur occurs almost invariably in the form 
of sulphates, compounds of sulphuric acid with metals, a 
class of bodies to be hereafter noticed. 

In plants, .sulphur is always present, though usually in 
small proportion. The turnip, the onion, mustard, horse- 
radish, and assafoetida owe their peculiar flavors to vola- 
tile oils of which sulphur is an ingredient. 



28 HOW CHOPS GROW. 

Albumin, globulin, casein and similar principles, never 
absent from plant or animal, possess also a small con- 
tent of sulphur. In hair and horn it occurs to the amount 
of three to five per cent. 

When organic matters are burned with full access of 
air, their sulphur is oxidized and remains in the ash as 
sulphates, or escapes into the air as sulphur dioxide. 

Phosphorus is an element which has such intense af- 
finities for oxygen that it never occurs naturally in the 
free state, and when prepared by art, is usually obliged to 
be kept immersed in water to prevent its oxidizing, or 
even taking fire. It is known to the chemist in the solid 
state in two distinct forms. In the more commonly oc- 
curring form, it is colorless or yellow, translucent, war- 
like in appearance ; is intensely poisonous, inflames by 
moderate friction, and is luminous in the dark ; hence its 
name, derived from two Greek words signifying light- 
tear er. The other form is brick-red, opaque, far less in- 
flammable, and destitute of poisonous properties. Phos- 
phorus is extensively employed for the manufacture of 
friction matches. For this purpose yellow phosphorus is 
chiefly used. When burned in air or in oxygen gas this ele- 
ment forms a white substance — phosphorus pentoxide 
(formerly termed anhydrous phosphoric acid) — which dis- 
solves in water, at the same time uniting chemically with 
a portion of the latter, and thus yielding a body of the 
utmost agricultural importance, viz., phosphoric acid. 

Exp. 18.— Burn a bit of phosphorus under a bottle, as in Exp. 8, omit- 
ting the water on the plate. The snow-like cloud of phosphorus pen- 
toxide gathers partly on the sides of the bottle, but mostly on the plate. 
It attracts moisture when exposed to the air, and hisses from develop- 
ment of heat when put into water. Dissolve a portion of it in hot 
water, and observe that the solution is acid to the taste. Finally evapo- 
rate the solution to dryness at a gentle heat. Instead of recovering 
thus the white opacpie phosphorus pentoxide, the residue is a trans- 
parent mass of phosphoric acid, a compound of phosphorus, oxygen 
and hydrogen. 

In nature phosphorus is usually found in the form of 



THE VOLATILE PART OF PLANTS. 29 

phosphates, which are phosphoric acid whose hydrogen 
has been partly or entirely replaced by metals. 

In plants and animals, it exists for the most part as 
phosphates of calcium (or lime), magnesium (or mag- 
nesia), potassium (or potash), and sodium (or soda). 

The bones of animals contain a considerable proportion 
(10 per cent.) of phosphorus, mainly in the form of cal- 
cium phosphate. It is from this that the phosphorus 
employed for matches is largely procured. 

Exp. 19.— Burn a piece of bone in a fire until it becomes white, or 
nearly so. The bone loses about half its weight. What remains is 
bone-earth or bone-ash, and of this 90 per cent, is calcium phosphate. 

Phosphates are readily formed by bringing together 

solutions of various metals with solution of phosphoric 
acid. 

Exp. 20. — Pour into each of two wine or test glasses a small quantity 
of the solution of phosphoric acid obtained in Exp. 18. To one, add 
some lime-water (see note p. 19) until a white cloud or precipitate is per- 
ceived. This is a calcium phosphate. Into the other portion drop solu- 
tion of alum. A translucent cloud of aluminium phosphate is immedi- 
ately produced. 

In soils and rocks, phosphorus exists in the state of 
phosphates of calcium, aluminium, and iron. 

The tissues and juices of animals and plants generally 
contain small proportions of several highly complex " or- 
ganic compounds" in which phosphoric acid is associated 
with the elements carbon, oxygen, hydrogen and nitrogen. 
Such substances are chlorophyll, lecithin and nuclein, 
to be noticed hereafter. 

We have thus briefly considered the more important 
characters of those six bodies which constitute that part 
of plants, and of animals also, which is volatile or de- 
structible at high temperatures, viz. : carbon, hydrogen, 
oxygen, nitrogen, sulphur, and phosphorus. 

Out of these substances, which are often termed the 
organic elements of vegetation, are chiefly compounded all 
the numberless products of life to be met with, either in 
the vegetable or animal world. 



30 HOW CROPS GROW. 

ULTIMATE COMPOSITION OF VEGETABLE MATTER. 

To convey an idea of the relative proportions in which 
these six elements exist in plants, a statement of the 
ultimate or elementary percentage composition of several 
kinds of vegetable matter is here subjoined. 

Grain of Straw of Tubers of Grain of Hay of Red 
Wlteat. Wheut. Potato. Peas. V lover. 

Carbon 46.1 48.4 44.0 46.5 47.4 

Hydrogen 5.8 5.3 5.8 6.2 5.0 

Oxygen 43.4 38.9 44.7 40.0 37.8 

Nitrogen 2.3 0.4 1.5 4.2 2.1 

Ash, including sulphur | 24 70 49 31 77 

and phosphorus ) 

100.0 100.0 100.0 100.0 100.0 

Sulphur 0.12 0.14 0.08 0.21 0.18 

Phosphorus 0.30 0.80 0.34 0.34 0.20 

Our attention may now be directed to the study of such 
compounds of these elements as constitute the basis of 
plants in general ; since a knowledge of them will pre- 
pare us to consider the remaining elements with a greater 
degree of interest. 

Previous to this, however, we must, first of all, gain a 
clear idea of that force — chemical affinity — in virtue of 
whose action these elements are held in their combina- 
tions and, in order to understand the language of chem- 
ical science, must know something of the views that now 
prevail as to the constitution of matter. 

§ 3. 

CHEMICAL AFFINITY. — THE ATOMIC-MOLECULAR THEORY. 

Chemical Attraction or Affinity is that force or 
kind of energy which unites or combines two or more sub- 
stances of unlike character, to a new body different from 
its ingredients. 

Chemical Combination differs essentially from mere 
mixture. Thus we may put together in a vessel the two 
gases, oxygen and hydrogen, and they will remain uncom- 
bined for an indefinite time, occupying their original vol- 



THE VOLATILE PART OF PLANTS. 31 

ume ; but if a flame be brought into the mixture they in- 
stantly unite with a loud explosion, and, in place of the 
light and bulky gases, we find a few drops of water, which 
is a liquid at ordinary temperatures, and in winter 
weather becomes solid, which does not sustain combus- 
tion like oxygen, nor itself burn as does hydrogen ; but 
is a substance having its own peculiar properties, differ- 
ing from those of all other bodies with which we are ac- 
quainted. 

In the atmosphere we have oxygen and nitrogen in a 
state of mere mixture, each of these gases exhibiting its 
own characteristic properties. When brought into chem- 
ical combination, they are capable of yielding a series of 
no less than live distinct compounds, one of which is the 
so-called laughing-gas, while the others form suffocating 
and corrosive vapors that are totally irrespirable. 

Chemical Decomposition. — Water, thus composed 
or put together by the exercise of affinity, is easily de- 
composed or taken to pieces, so to speak, by forces that 
oppose affinity — e. g., heat and electricity — or by the 
greater affinity of some other body — e. g. , sodium— as al- 
ready illustrated in the preparation of hydrogen, Exp. 11. 

Definite Proportions. — A further distinction be- 
tween chemical union and mere mixture is, that, while 
two or more bodies may, in general, be mixed in all pro- 
portions, bodies combine chemically in comparatively 
few proportions which are fixed and invariable. Oxygen 
and hydrogen, e. g., are found united in nature, princi- 
pally in the form of water ; and water, if pure, is always 
composed of one-ninth hydrogen and eight-ninths oxy- 
gen by weight, or, since oxygen is, bulk for bulk, sixteen 
times heavier than hydrogen, of one volume or measure 
of oxygen to two volumes of hydrogen. 

Atoms. — It is now believed that matter of all kinds 
consists of indivisible and unchangeable particles called 
atoms, which are united to each other by chemical at- 



32 HOW CROPS GROW. N 

traction, and cannot ordinarily exist in the free state. 
On this view each particular kind of matter or chemical 
substance owes its individuality either to the special kinds 
or to the numbers of the atoms it consists of. Atoms 
may be defined as the smallest quantities of matter which 
can exist in chemical combination and the smallest of 
which we have any knowledge or conception. 

Atomic Weight of Elements. — On the hypothesis 
that chemical union takes place between atoms of the 
elements, the simplest numbers expressing the propor- 
tions by weight* in which the elements combine, are ap- 
propriately termed atomic weights. These numbers are 
only relative, and since hydrogen is the element which 
unites in the smallest proportion by weight, it is assumed 
as the standard unit. From the results of a great 
number of the most exact experiments, chemists have 
generally agreed upon the atomic weights given in the 
subjoined table for the elements already mentioned or 
described. 

Symbols. — For convenience in representing chemical 
changes, the first letter (or letters) of the Latin name 
of the element is employed instead of the name itself, and 
is termed its symbol. 

TABLE OF ATOMIC WEIGHTS AND SYMBOLS OF ELEMENTS.t 

Element. Atomic Weight. Symbol. 

Hydrogen 
Carbon 
Oxygen 
Nitrogen 
Sulphur 
Phosphorus 
Chlorine 
Mercury 
Potassium 
Sodium 
Calcium 
Iron 



1 


H 


12 


C 


16 


o 


14 


N 


32 


S 


31 


P 


35.5 


CI 


200 


Hg (Hydrargyrum) 


39 


K (Kalium) 


23 


Na (Natrium) 


40 


Ca 


56 


Fe (Ferrum) 



* Unless otherwise stated, parts or proportions by weight are always 
to be understood. 

t Now, chemists receive as the true atomic weights double the num- 
bers that were formerly employed, those of hydrogen, chlorine and a 
few others excepted. The atomic weights here given are mostly whole 
numbers. The actual atomic weights, as experimentally determined, 
differ from the above by small fractions, which may be neglected. 



THE VOLATILE PART OF PLANTS. 33 

Multiple Proportions. — When two or more bodies 
unite in several proportions, their quantities, when not 
expressed by the atomic weights, are twice, thrice, four, 
or more times, these weights ; they are multiples of the 
atomic weights by some simple number. Thus, carbon 
and oxygen form two commonly occurring compounds, 
viz., carbon monoxide, consisting of one atom of each in- 
gredient, and carbon dioxide, which contains to one atom, 
or 12 parts by weight, of carbon, two atoms, or 32 parts 
by weight, of oxygen. 

Molecules* contain and consist of chemically-united 
atoms, and are the smallest particles of matter that can 
have an individual or physical existence. While the 
atoms compose and give character to the molecules, the 
molecules alone are sensibly known to us, and they give 
character to matter as we find it in masses, either solid, 
liquid or gaseous. In solids the molecules more or less 
firmly cohere together ; in liquids they have but little 
cohesion, and in gases they are far apart and tend to sepa- 
rate from each other. The so-called "elements" are, in 
fact, mostly compounds whose molecules consist of two 
or more like atoms, while all other chemical substances 
are compounds whose molecules are made up of two or 
more unlike atoms. 

Molecular Weights of Compounds. — The mole- 
cular weight of a compound is the sum of the weights of 
the atoms that compose it. For example, water being 
composed of 1 atom, or 16 parts by weight, of oxygen, 
and 2 atoms, or 2 parts by weight, of hydrogen, has the 
molecular weight of 18. f 

The following scheme illustrates the molecular compo- 
sition of a somewhat complex compound, one of the car- 

* Latin diminutive, signifying a little mass. 

t We must refer to recent treatises on chemistry for fuller informa- 
tion as to atoms and molecules and the methods of finding the atomic 
and molecular weights. 

3 



34 HOW CROPS GROW. 

bonates of ammonium, which consists of four elements, 
ten atoms, and has a molecular weight of seventy-nine. 

Ammonia gas results from the union of an atom of 
nitrogen with three atoms of hydrogen. One molecule 
of ammonia gas unites with a molecule of carbon dioxide 
gas and a molecule of water to produce a molecule of 
ammonium carbonate. 

Atoms. Atomic Molecular 
weights, weights. 



Ammonium 

Carbonate 

1 mol. 



il I ="1 



Ammonia _ i Hydrogen, 3 

1 mol. ~~ ( Nitrogen, 1 

Carbon di- _ ( Carbon, 1 = 12 ) ., 

oxide 1 mol. - { Oxygen, 2 = 32 ' 

Water, _ ( Hydrogen, 2 

1 mol. - | Oxygen, 1 



=79 



= 16 | = 18 , 

Notation and Formulas of Compounds. — For the 
purpose of expressing easily and concisely the composi- 
tion of compounds, and the chemical changes they 
undergo, chemists have agreed to make the symbol of an 
element signify one atom of that element. 

Thus H implies not only the light, combustible gas 
hydrogen, but also one part of it ly weight as compared 
with other elements, and S suggests, in addition to the 
idea of the body sulphur, the idea of 32 parts of it by 
weight. Through this association of the atomic weight 
with the symbol, the composition of compounds is 
expressed in the simplest manner by writing the symbols 
of their elements one after the other. Thus, carbon 
monoxide is represented by 00, mercuric oxide by HgO, 
and iron .monosulphide by FeS. The symbol 00 con- 
veys to the chemist not only the fact of the existence 
of carbon monoxide, but also instructs him that its mole- 
cule contains an atom each of carbon and of oxygen, and 
from his knowledge of the atomic weights he gathers the 
proportions by weight of the carbon and oxygen in it. 

When a compound contains more than one atom of an 
element, this is shown by appending a small figure to the 
symbol of the latter. For example : water consists of 
two atoms of hydrogen united to one of oxygen, and its 



THE VOLATILE PART OF PLAN/TS. 35 

symbol is H 2 0. In like manner the symbol of carbon 
dioxide is C0 2 . 

When it is wished' to indicate that more than one mole- 
cule of a compound exists in combination or is concerned 
in a chemical change, this is done by prefixing a large 
figure to the symbol of the compound. For instance, 
two molecules of water are expressed by 2 H 2 0. 

The symbol of a compound is usually termed & formula 
and if correct is a molecular formula and shows the com- 
position of one molecule of the substance. Subjoined is 
a table of the molecular formulas of some of the com- 
pounds that have been already described or employed. 

FORMULAS OF COMPOUNDS. 

Name. 

Water 

Hydrogen Sulphide 
Iron Monosulphide 
Mercuric Oxide 
Carbon Dioxide 
Calcium Chloride 
Sulphur Dioxide 
Sulphur Trioxide 
Phosphorus Pentoxide 

Empirical and Rational Formulas. — It is obvious 
that many different formulas can be made for a body of 
complex character. Thus, the carbonate of ammonium, 
whose composition has already been stated (p. 33), and 
which contains 

1 atom of Nitrogen, 
1 atom of Carbon, 
3 atoms of Oxygen, and 
5 atoms of Hydrogen, 

may be most compactly expressed by the symbol 

nco s h 5 . 

Such a formula merely informs us what elements and 
how many atoms of each element enter into the compo- 
sition of the substance. It is an empirical formula, 
being the simplest expression of the facts obtained by 
analysis of the substance. 

Rational formulas, on the other hand, are intended to 
convey some notion as to the constitution, formation, or 



Formula. 


Molecular Weight. 


H 2 


18 


H 2 S 


34 


FeS 


88 


HgO 


216 


co 2 

CaCl 2 


44 


111 


so 2 


64 


so. 


80 


rA 


142 



3G HOW CROPS GROW. 

modes of decomposition of the body. For example, the 
real arrangement of the atoms in ammonium carbonate 
is believed to be expressed by the rational (or structural) 
formula 

_ c /0-N H 4 

U=t \0— H 

in which the carbon is directly united to oxygen, to 
which latter one hydrogen and the nitrogen are also 
linked, the remaining hydrogens being combined to the 
nitrogen. 

Valence. — The connecting lines or dashes in the fore- 
going formula show the valence of the several atoms, i. e. , 
their "atom-fixing power." The single dash from H 
indicates that hydrogen is univalent or lias a valence of 
one. The two dashes connected with express the 
bivalence of oxygen or that the atom of this element can 
combine with two hydrogens or other univalent atoms. 
The nitrogen is united on one hand with 4 hydrogen 
atoms, and also, on the other hand, satisfies half the val- 
ence of oxygen ; it is accordingly quinquivalent, i. e., has 
five units of valence. Carbon is quadrivalent, being 
joined to oxygen by four units of valence. 

Equations of Formulas serve to explain the results 
of chemical reactions and changes. Thus, the breaking 
up by heat of potassium chlorate into potassium chloride 
and oxygen is expressed by the following statement: 

Potassium Chlorate. Potassium Chloride. Oxygen. 

2 KC10 3 = 2 KC1 + 3 2 

The sign of equality, =, shows that what is written 
before it supplies and is resolved into what follows it. 
The sign -f- indicates and distinguishes separate com- 
pounds. 

The employment of this kind of short-hand for exhib- 
iting chemical changes will find frequent illustration as 
we proceed with our subject. 

Modes of Stating Composition of Chemical 



THE VOLATILE PART OF PLANTS. 37 

Compounds. — These are two: 1, atomic or molecular 
statements, and 2, centesimal statements, or proportions 
in one hundred parts (per cent, p. c, or %). These 
modes of expressing composition are very useful for com- 
paring together different compounds of the same ele- 
ments, and, while usually the atomic statement answers 
for substances which are comparatively simple in their 
composition, the statement per cent is more useful for 
complex bodies. The composition of the two compounds 
of carbon with oxygen is given below according to both 
methods. 

Atomic. Per cent. Atomic. Percent. 

Carbon (C), 12 42.86 (C) 12 27.27 

Oxygen (O), 16 57.14 (0 2 ) 32 72.73 

Carbon Monoxide (CO), 28 100.00 Carbon Dioxide (C0 2 ), 44 100.00 

The conversion of one mode of statement into the other is a case of 
simple rule of three, which is illustrated in the following calculation 
of the centesimal composition of water from its molecular formula. 

Water, H 2 0, has the molecular weight 18, i. e., it consists of two 
atoms of hydrogen, or two parts, and one atom of oxygen, or sixteen 
parts by weight. 

The arithmetical proportions subjoined serve for the calculation, viz. : 

H 2 Water H Hydrogen 

18 ; 100 ! I 2 ; per cent sought (=11.11) 

H 2 Water O Oxvgen 

18 : 100 I I 16 : per cent sought (=88.89) 

By multiplying together the second and third terms of these propor- 
tions, and dividing by the first, we obtain the requiredper cent, viz., of 
hydrogen, 11.11 ; and of oxygen, 88.89. 

The reader must bear well in mind that chemical affin- 
ity manifests itself with very different degrees of inten- 
sity between different bodies, and is variously modified, 
excited, or annulled, by other natural agencies and forces, 
especially by heat, light and electricity. 

§ 4 - 

VEGETABLE ORGANIC COMPOUNDS, OR PROXIMATE 
PRINCIPLES. 

We are now prepared to enter upon the study of the 
organic compounds, which constitute the vegetable struc- 



38 HOW CROPS GROW. 

ture, and which are produced from the elements carbon, 
oxygen, hydrogen, nitrogen, sulphur, and phosphorus, by 
chemical agency. The number of distinct substances 
found in plants is practically unlimited. There are 
already well known to chemists hundreds of oils, acids, 
bitter principles, resins, coloring matters, etc. Almost 
every plant contains some organic body peculiar to itself, 
and usually the same plant in its different parts reveals 
to the senses of taste and smell the presence of several 
individual substances. In tea and coffee occurs an 
intensely bitter " active principle," caffeine. From 
tobacco an oily liquid of eminently narcotic and poison- 
ous properties, nicotine, can be extracted. In the orange 
are found no less than three oils ; one in the leaves, one 
in the flowers, and a third in the rind of the fruit. 

Notwithstanding the great number of bodies thus 
occurring in the vegetable kingdom, it is a few which 
form the bulk of all plants, and especially of those which 
have an agricultural importance as sources of food to 
man and animals. These substances, into which any 
plant may be resolved by simple, partly mechanical means, 
are conveniently termed proximate princivles, and we 
shall notice them in some detail under eight principal 
classes, viz. : 

1. Water. 

2. The Carbhydrates. 

3. The Vegetable Acids. 

4. The Fats and Oils. 

5. The Albuminoids or Protein Bodies and Fer- 
ments. 

6. The Amides. 

7. The Alkaloids. 

8. Phosphorized Substances. 

i. Water, H 2 0, as already stated, is the most abund- 
ant ingredient of plants. It is itself a compound of 
oxygen and hydrogen, having the following centesimal 
composition : 



THE VOLATILE PART OF PLANTS. 39 



Oxygen 88.89 

Hydrogen 11-11 

100.00 

It exists in all parts of 'plants, is the immediate cause 
of the succulence of their tender portions, and is essen- 
tial to the life of the vegetable organs. 

In the following table are given the percentages of water in some of 
the more common agricultural products in the fresh state, but the pro- 
portions are not quite constant, even in the same part of different 
specimens of any given plant. 

WATER IN FRESH PLANTS. (PER CENT.) 

Average. Range. 

Meadow grass 71 60 to 78 

Red clover 80 68 "86 

Maize, as used for fodder 82 71 "93 

Cabbage 85 80 "94 

Potato tubers 75 77 82 

Sugar beets 81 76 "90 

Carrots 86 79 "90 

Turnips 91 86 "93 

In living plants, water is usually perceptible to the 
eye or feel, as sap. But it is not only fresh plants that 
contain water. "When grass is made into hay, the water 
is by no means all dried out, but a considerable propor- 
tion remains in the pores, which is not recognizable by 
the senses. So, too, seasoned wood, flour, and starch, 
when seemingly dry, contain a quantity of invisible 
water, which can be removed by heat. 

Exp. 21.— Into a wide glass tube, like that shown in Fig. 2, place a 
spoonful of saw dust, or starch, or a little hay. Warm over a lamp, 
but very slowly and cautiously, so as not to burn or blacken the sub- 
stance. Water will be expelled from the organic matter, and will col- 
lect on the cold part of the tube. 

It is thus obvious that vegetable substances may con- 
tain water in at least two different conditions. Red 
clover, for example, when growing or , _ ffl 

freshly cut, contains about 80 per cent of 
water. When the clover is dried, as for 
making hay, the greater share of this wa- N| 
ter escapes, so that the air-dry plant con- 



tains but about 15 per cent. On subject- 
ing the air-dry clover to a temperature 
of 212 ° for some hours, the water is completely expelled, 
and the substance becomes really dry. i. e., water-free. 



40 HOW CROPS GROW. 

To drive off all water from vegetable matters, the chemist usually 
employs a water-oven, Fig. 9, consisting of a vessel of tin or copper 
plate, with double walls, between which is a space that may be half 
filled with water. The substance to be dried is placed in the interior 
chamber, the door is closed, and the water is brought to boil by the 
heat of a lamp or stove. The precise quantity of water belonging to, 
or contained in, a substance, is ascertained by first weighing the sub- 
stance, then drying it until its weight is constant. The loss is water. 

In the subjoined table are given the average quantities, per cent, of 
water existing in various vegetable products when air-dry. 

WATER IN AIR-DRY PLANTS. PER CENT. 

Meadow grass (hay) 15 

Red clover hay 17 

Pine wood 20 . 

Straw and chaff of wheat, rye, etc 15 * 

Bean straw 18 

Wheat (rye, oat) kernel 14 

Maize kernel 12 

That portion of the water which the fresh plant loses 
by mere exposure to the air is chiefly the water of its 
juices or sap, and, on crushing the fresh plant, is mani- 
fest to the sight and feel as a liquid. It is, properly speak- 
ing, the free water of vegetation. The water which 
remains in the air-dry plant is imperceptible to the senses 
while in the plant, — can only be discovered on expelling 
it by heat or otherwise, — and may be designated as the 
hygroscopic or combined water of vegetation. 

The amount of water contained in either fresh or air- 
dry vegetable matter is somewhat fluctuating, according 
to the temperature and the dryness of the atmosphere. 

2. The Carbhydrates. This group falls into three 
subdivisions, viz. : 

a. The Amyloses, comprising Cellulose, Starch, Inu- 
lin, Glycogen, the Dextrins and Gums, having the 
formula (C G H 10 5 )n. 

b. The Glucoses, which include Dextrose, Levulose, 
Galactose and similar sugars, having the composition 
6 H 12 6 . 

c. The Sucroses, viz. : Cane Sugar or Saccharose, 
Maltose, Lactose and other sugars, whose formula in 
most cases is Ci 2 H 22 0n. 



THE VOLATILE PART OF PLANTS. 



41 



On account of their abundance and uses the Carbhy- 
drates rank as the most important class of vegetable sub- 
stances. Their name refers to the fact that they consist 
of Carbon, Hydrogen and Oxygen, the last two elements 
being always present in the same proportions that are 
found in water. 

These bodies, especially cellulose and starch, form by 
far the larger share — perhaps seven-eighths — of all the dry 
matter of vegetation, and most of them are distributed 
throughout all parts of plants. 

a. The Amyloses. 

Cellulose (C 6 H 10 O 5 )n. — Every agricultural plant is 
an aggregate of microscopic cells, i. e., is made up of 
minute sacks or closed tubes, adhering to each other. 

Fig. 10 represents an extremely thin slice from the stem of a cabbage, 
magnified 230 diameters. The united walls of two cells are seen in sec- 
tion at a, while at b an empty space is noticed. 




Fig. 10. 



The outer coating, or wall, of the vegetable cell con- 
sists chiefly or entirely of cellulose. This substance is 
accordingly the skeleton or framework of the plant, and 
the material that gives toughness and solidity to its parts. 
Next to water it is the most abundant body in the vege- 
table world. 



42 



HOW CROPS GROW. 



Nearly all plants and all their parts contain cellulose, 
but it is relatively most abundant in 
stems and leaves. In seeds it forms a 
large portion of the husk, shell, or other 
outer coating, but in the interior of the 
seed it exists in small proportion. 

The fibers of cotton (Fig. 11, a), hemp, 
and flax (Fig. 11, b), and white cloth and 
unsized paper made from these materials, 
are nearly pure cellulose. 

The fibers of cotton, hemp, and flax are simply 
long and thick-walled cells, the appearance of 
which, when highly magnified, is shown in Fig. 11, 
where a represents the thinner, more soft, and col- 
lapsed cotton fiber, and b the thicker and more dur- 
able fiber of linen. 

Wood, or woody fiber, consists of long 
and slender cells of various forms and di- 
mensions (see p. 293), which are delicate 
when young (in the sap wood), but as 
they become older fill up interiorly by the deposition of re- 
peated layers of cellulose, which is more or less inter- 
grown with other substances.* The hard shells of nuts 
and stone fruits contain a basis of cellulose, which is im- 
pregnated with other matters. 

When quite pure, cellulose is a white, often silky or 
spongy, and translucent body, its appearance varying 

* Wood was formerly supposed to consist of cellulose and so-called 
"lignin." On this view, according to F. Schulze, lignin impregnates 
(not simply incrusts) the cell-wall, is -soluble in hot alkaline solutions, 
and is readily oxidized by nitric acid. Schulze ascribes to it the com- 
position 

Carbon 55.3 

Hydrogen 5.8 

Oxygen 38.9 




Fi-. 11. 



100.0 



This is, however, simply the inferred composition of what is left after 
the cellulose, etc., havebeen removed. " Lignin " cannot be separated 
in the pure state, and has never been analyzed. What is thus desig- 
nated is a mixture of several distinct substances. Fremy's lignose, lig- 
none, lignin, and lignireose, as well as J. Erdman's glycolignose and 
lignose, are not established as chemically distinct substances. 



THE VOLATILE PART OF PLANTS. 43 

somewhat acc6rding to the source whence it is obtained. 
In the air-dry state, at common temperatures, it usually 
contains about 10 % of hygroscopic water. It has, in 
common with animal membranes, the character of swell- 
ing up when immersed in water, from imbibing this 
liquid ; on drying again, it shrinks in bulk. It is tough 
and elastic. 

Cellulose, as it naturally occurs, for the most part dif- 
fers remarkably from the other bodies of this group, in 
the fact of its slight solubility in dilute acids and alkalies. 
It is likewise insoluble in water, alcohol, ether, the oils, 
and in most ordinary solvents. It is hence prepared in 
a state of purity by acting upon vegetable tissues con- 
taining it, with successive solvents, until all other mat- 
ters are removed. 

The "skeletonized" leaves, fruit vessels, etc., which compose those 
beautiful objects called x>liantom bouquets, are commonly made by dis- 
solving away the softer portions of fresh succulent plants by a hot solu- 
tion of caustic soda, and afterwards whitening the skeleton of fibers 
that remains by means of chloride of lime (bleaching powder). They 
are almost pure cellulose. 

Skeletons may also be prepared by steeping vegetable matters hi a 
mixture of potassium chlorate and dilute nitric acid for a number of 
days. 

Exp. 22.— To 500 cubic centimeters* (or one pint) of nitric acid of dens- 
ity 1.1, add 30 grams (or one ounce) of pulverized potassium chlorate, 
and dissolve the latter by agitation. Suspend in this mixture a num- 
ber of leaves, etc.,t and let them remain undisturbed, at a temperature 
not above 65° F., until they are perfectly whitened, which may require 
from 10 to 20 days. The skeletons should be floated out from the 
solution on slips of paper, washed copiously in clear water, and dried 
under pressure between folds of unsized paper. 

The fibers of the whiter and softer kinds of wood are now much em- 
ployed in the fabrication of paper. For this purpose the wood is rasped 



* On subsequent pages we shall make frequent use of some of the 
French decimal weights and measures, for the reasons that they ate 
much more convenient than the English ones, and are now almost ex- 
clusively employed in all scientific treatises and investigations. For 
small weights, the gram, abbreviated gm. (equal to 15£ grains, nearly), 
is the customary unit. The unit of measure by volume is the ctibic cen- 
timeter, abbreviated c. c. (30 c. c. equal one fluid ounce nearly). Gram 
weights and glass measures graduated into cubic centimeter's are fur- 
nished by all dealers in chemical apparatus. 

t Full-grown but not old leaves of the elm, maple, and maize, heads of 
unripe grain, slices of the stem and joints of maize, etc., may be em- 
ployed to furnish skeletons that will prove valuable in the study of the 
structure of these organs. 



44 HOW CROPS GROW. 

to a coarse powder by machinery, then heated with a weak soda lye, 
and finally bleached with chloride of lime. 

Though cellulose is insoluble in, or but slightly affected 
by, weak or dilute acids and alkalies, it is altered and dis- 
solved by these agents, when they are concentrated or 
hot. The result of the action of strong acids and alka- 
lies is various, according to their kind and the degree of 
strength in which they are employed. 

Cellulose Nitrates. —Strong nitric acid transforms 
cellulose into various cellulose nitrates according to its 
concentration. In these bodies portions of the hydrogen 
and oxygen of cellulose are replaced by the atomic group 
(radicle), N0 3 . Cellulose hexanitrate, Ci 2 H 14 (NO 3 ) 6 O 10 , 
is employed as an explosive under the name gun cotton. 
The collodion employed in photography is a solution 
in ether of the penta- and tetranitrates, Ci 2 H 15 (lsr03) 5 Oio 
and Ci2H 16 (N0 3 ) 4 Oio. Sodium hydroxide changes these 
cellulose nitrates into cellulose and sodium nitrate. 

Hot nitric acid of ordinary strength destroys cellulose 
by oxidizing it with final formation of carbon dioxide 
gas and oxalic acid. 

Cellulose Sulphates. — When cold sulphuric acid 
acts on cellulose the latter may either remain apparently 
unaltered or swell up to a pasty mass, or finally dissolve 
to a clear liquid, according to the strength of the acid, 
the time of its action, and the quality (density) of the 
cellulose. In excess of strong oil of vitriol, cellulose 
(cotton) gradually dissolves with formation of various 
cellulose sulphates, in which OH groups of the cellulose 
are replaced by S0 4 of sulphuric acid. These sulphates 
are soluble in water and alcohol, and when boiled with 
water easily decompose, reproducing sulphuric acid, but 
not cellulose. Instead of the latter, dextrin and dextrose 
(grape sugar) appear. 

Soluble Cellulose, or Amyloid. — In a cooled mix- 
ture of oil of vitriol, with about i its volume of water, 



THE VOLATILE PART OF PLANTS. 45 

cellulose dissolves. On adding much water to the solu- 
tion there separates a white substance which has the same 
composition as cellulose, but is readily converted into 
dextrin by cold dilute acid. This form of cellulose as- 
sumes a fine blue color when put in contact with iodine- 
tincture and sulphuric acid. 

Exp. 23.— Fill a large test-tube first with water to the depth of two or 
three inches. Then add gradually three times that bulk of oil of vitriol, 
and mix thoroughly. When well cooled pour a part of the liquid on a 
slip of unsized paper in a saucer. After some time the paper is seen to 
swell up and partly dissolve. Now flow it with solution of iodine,* 
when these dissolved portions will assume a fine and intense blue color. 
This deportment is characteristic of cellulose, and may be employed 
for its recognition under the microscope. If the experiment be re- 
peated, using a larger proportion of acid, and allowing the action to 
continue for a considerably longer time, the substance producing the 
blue color is itself destroyed, and addition of iodine has no effect.f Un- 
altered cellulose gives with iodine a yellow color. 

Paper superficially converted into amyloid constitutes vegetable 
parchment, which is tough and translucent, much resembling bladder, 
and very useful for various purposes, among others as a substitute for 
sausage "skins." 

Exp. 24.— Into the remainder of the cold acid of Exp. 23 dip a strip of 
unsized paper, and let it remain for about 15 seconds ; then remove, and 
rinse it copiously in water. Lastly, soak some minutes in water, to 
which a little ammonia is added, and Avash again with pure water. 
These washings are for the purpose of removing the acid. The success 
of this process for obtaining vegetable parchment depends upon the 
proper strength of the acid, and the time of immersion. If need be, 
repeat, varying these conditions slightly, until the result is obtained. 

The denser and more impure forms of cellulose, as they 
occur in wood and straw, are slowly acted upon by chem- 
ical agents, and are not easily digestible by most animals ; 
but the cellulose of young and succulent stems, leaves, 
and fruits is digestible to a large extent, especially by 
animals which naturally feed on herbage, and therefore 
cellulose is ranked among the nutritive ingredients of 
cattle-food. 

Chemical composition of cellulose. — This body is acom- 



* Dissolve a fragment of iodine as large as a wheat kernel in 20 c. c. of 
alcohol, and add 100 c. c. of water to the solution. 

t According to Grouven. cellulose prepared from rye straw (and im- 
pure?) requires several hours' action of sulphuric acid before it will 
strike a blue color with iodine (2tcr Salzmiinaer Bericht, p. 467). 



46 HOW CROPS GROW. 

pound of the three elements, carbon, oxygen, and hydro- 
gen. Analyses of it, as prepared from a multitude of 
sources, demonstrate that its composition is expressed by 
the formula (C 6 Hi 5 )n. The value of n in this form- 
ula is not certainly known, but is at least two, and the 
formula Ci 2 H 2 oOio is very commonly adopted. In 100 
parts it contains 

Carbon 44.44 

Hydrogen 6.17 

Oxygen 49.39 

100.00 
Modes of estimating cellulose.— In statements of the composition of 
plants, the terms fiber, woody fiber, and crude cellulose are often met 
with. These are applied to more or less impure cellulose, which is ob- 
tained as a residue after removing other matters, as far as possible, by 
alternate treatment with dilute acids and alkalies. The methods are 
confessedly imperfect, because cellulose itself is dissolved to some ex- 
tent, and a portion of other matters often remains unattacked. 

The method of Henneberg, usually adopted ( Vs. St., YI, 497), is as follows : 
3 grams of the finely divided substance are boiled for half an hour with 
200 cubic centimeters of dilute sulphuric acid (containing 1J per cent of 
oil of vitriol), and, after the substance has settled, the acid liquid is 
poured off. The residue is boiled again for half an hour with 200 c. c. of 
dilute potash lye (containing 1\ per cent of dry caustic potash), and, after 
removing the alkaline liquid, it is boiled twice with water as before. 
What remains is brought upon a filter, and washed with water, then 
with alcohol, and, lastly, with ether, as long as these solvents take 
up anything. This crude cellulose contains ash and nitrogen, for Avhich 
corrections must be made. The nitrogen is assumed to belong to some 
albuminoid, and from its quantity the amount of the latter is calcu- 
lated; (seep. 113). 

Even with these corrections, the quantity of cellulose is not obtained 
with entire accuracy, as is usually indicated by its appearance and its 
composition. While the crude cellulose thus prepared from the pea is 
perfectly white, that from wheat bran is brown, and that from rape- 
cake is almost black in color, from impurities that cannot be removed 
by this method. 

Grouven gives the following analyses of two samples of crude cellu- 
lose obtained by a method essentially the same as we have described. 
(2ter Salzmiinder Bericht, p. 456.) 

Rye-straw fiber. Flax fiber. 

Water 8.65 5.40 

Ash 2.05 1.14 

N 0.15 0.15 

C 42.47 38.36 

H 6.04 5.89 

40.64 48.95 

100.00 100.00 

On deducting water and ash, and making proper correction for the 



THE VOLATILE PART OF PLANTS. 47 



nitrogen, the above samples, together with one of wheat-straw fiber, 
analyzed by Henneberg, exhibit the following composition, compared 
with pure cellulose. 

Rye-straw fiber. Flax fiber. Wheat-straw fiber. Pure cellulose. 

C 47.5 41.0 45.4 44.4 

H 6.8 6.4 6.3 6.2 

O 46.7 02.6 48.3 49.4 



100.0 100.0 100.0 100.0 

Fr. Schulze has proposed (1857) another method for estimating cellu- 
lose, which, though troublesome, is in most cases more correct than the 
one already described. Kuhn, Aronstein, and H. Schulze (Henneberg's 
Journal fur La lahvirthschaft, 1866, pp. 289 to 297) have applied this 
method in the following manner : One part of the dry pulverized sub- 
stance (2 to 4 grams), which has been previously extracted with water, 
alcohol, and ether, is placed in a glass-stoppered bottle, with 0.8 part 
of potassium chlorate and 12 parts of nitric acid of specific gravity 1.10, 
and digested at a temperature not exceeding 65° F. for 14 days. At the 
expiration of this time, the contents of the bottle are mixed with some 
water, brought upon a filter, and washed, firstly, with cold and after- 
wards with hot water. When all the acid and soluble matters have 
been washed out, the contents of the filter are emptied into a beaker, 
and heated to 165° F. for about 45 minutes with weak ammonia (1 part 
commercial ammonia to 50 parts of water); the substance is then 
brought upon a weighed filter, and washed, first, with dilute ammonia, 
as long as this passes off colored, then with cold and hot water, then 
with alcohol, and, finally, with ether. The substance remaining con- 
tains a small quantity of ash and nitrogen, for which corrections must 
be made. The fiber is, however, purer than that procured by the other 
method, and the writers named obtained a somewhat larger quantity, 
by 5 to \h per cent. The results appear to vary but about one per cent 
from the truth. The observations of Konig (Vs. St. 16), and of Hoffmeis- 
ter (Vs. St. 33, 155), show much larger differences in favor of Fr. Schulze's 
method. 

Hugo Miiller (Die Pflanzenf aser, p. 27) has described a method of ob- 
taining cellulose from those materials which are employed in paper- 
making, which is based on the prolonged use of weak aqueous solu- 
tion of bromine. 

Trials made on hay and Indian-corn fodder with this method by Dr. 
Osborne, at the author's suggestion, gave results widely at variance 
with those obtained by Henneberg's method. 

The average proportions of cellulose found in various 
vegetable matters, in the usual'or air-dry state, are as fol- 
lows : 

AMOUNT OF CELLULOSE IN PLANTS. 

Per cent. Per cent 

Potato tuber 1.1 Red clover plant in flower — 10 

Wheatkernel 3.0 " " hay 34 

Wheat meal 0.7 Timothy 23 

Maize kernel 5.5 Maize cobs 38 

Barley " 8.0 Oat straw 40 

Oat " 10.3 Wheat" 48 

Buckwheat kernel 15.0 Rye " 54 



48 HOW CROPS GROW. 

Starch (C 6 H 10 5 )n is of very general occurrence in 
plants. The cells of the seeds of wheat, corn, and all 
other grains, and the tubers of the potato, contain this 
familiar body in great abundance. It occurs also in the 
wood of all forest trees, especially in autumn and winter. 
Ifc accumulates in extraordinary quantity in the pith of 
some plants, as in the Sago-palm (Sagus Rumphii), of 
the Malay Islands, a single tree of which may yield 800 
pounds. The onion, and various plants of the lily tribe, 
are said to be entirely destitute of starch. 

The preparation of starch from the potato is very sim- 
ple. The potato tuber contains about 70 per cent, water, 
24 per cent starch, and 1 per cent of cellulose, while the 
remaining 5 per cent consist mostly of matters which 
are easily soluble in water. By grating, the potatoes are 
reduced to a pulp; the cells are thus broken and the 
starch-grains set at liberty. The pulp is agitated on a 
fine sieve, in a stream of water. The washings run off 
milky from suspended starch, while the cell-tissue is re- 
tained by the sieve. The milky liquid is allowed to rest 
in vats until the starch is deposited. The water is then 
poured off, and the starch is collected and dried. 

Wheat-starch may be obtained by allowing wheaten 
flour mixed with water to ferment for several weeks. In 
this process the gluten, etc., are converted into soluble 
matters, which are removed by washing, from the unal- 
tered starch. 

Starch is now most largely manufactured from maize. 
A dilute solution of caustic soda is used to dissolve the 
albuminoids (see p. 87). The starch and bran remaining 
are separated by diffusing both in water, when the bran 
rapidly settles, and the water, being run off at the proper 
time, deposits nearly pure starch, the corn-starch of com- 
merce. 

Starch is prepared by similar methods from rice, horse- 
chestnuts, and various other plants. 



THE VOLATILE PART OF PLANTS. 



49 



Arrow-root is starch obtained by grating and washing 
the root-sprouts of Maranta Indica, and M. arandinacea, 
plants native to the East and West Indies. 

Exp. 25.— Reduce a clean potato to pulp by means of a tin grater. Tie 
up the pulp in a piece of not too fine muslin, and scpieeze it repeatedly 
in a quart or more of water. The starch grains thus pass the meshes of 
the cloth, while the cellulose is retained. Let the liquid stand until 
the starch settles, pour off the water, and dry the residue. 

Starch, as usually seen, is either a white powder which 
consists of minute, rounded grains, and hence has a 
slightly harsh feel, or occurs in 5 or 6-sided columnar 
masses which readily crush to a powder. Columnar 
starch acquires that shape by rapid drying of the wet 
substance. When observed under a powerful magnifier, 
the starch-grains often present characteristic forms and 
dimensions. 

In potato-starch they are egg or kidney-shaped, and 
are distinctly marked with curved lines or ridges, which 




Fig. 12. 

surround a point or eye ; a, Fig. 12. Wheat-starch con- 
sists of grains shaped like a thick burning-glass, or spec- 
tacle-lens, having a cavity in the centre, i. Oat-starch 
is made up of compound grains, which are easily crushed 
into smaller granules, c. In maize and rice the grains 
are usually so densely packed in the cells as to present an 
angular (six-sided) outline, as in d. The starch of the 
bean and pea has the appearance of e. The minute 



50 HOW CROPS GROW. 

starch-grains of the parsnip are represented at /, and 
those of the beet at g. 

The grains of potato-starch are among the largest, be- 
ing often ^£ <j of an inch in diameter ; wheat-starch 
grains are about y^^ of an inch ; those of rice, ^jfov °f 
an inch, while those of the beet-root are still smaller. 

The starch-grains have an organized structure, plainly 
seen in those from the potato, which are marked with 
curved lines or ridges surrounding a point or eye ; a, Fig. 
12. When a starch-grain is heated cautiously, it swells 
and exfoliates into a series of more or less distinct layers. 

Starch, when air-dry, contains a considerable amount of 
water, which may range from 12 to 23 per cent. Most of 
this water escapes readily when starch is dried at 212°, 
but a temperature of 230° F. is needful to expel it com- 
pletely. Starch, thus dried, has the same composition 
in 100 parts as cellulose, viz. : 

Carbon 44.44 

Hydrogen 6.17 

Oxygen 49.39 

100.00 

Starch-grains are unacted upon by cold water, unless 
broken (see Exp. 26), and quickly settle from suspension 
in it, having a specific gravity of 1.5. 

Iodine-Test for Starch. — The chemist is usually able to 
recognize starch with the greatest ease and certainty by 
its peculiar deportment towards iodine, which, when dis- 
solved in water or alcohol and brought in contact with 
starch-grains, most commonly gives them a beautiful 
blue or violet color. This test may be used even in 
microscopic observations with the utmost facility. Some 
kinds of starch-grains are, however, colored red, some 
yellow, and a few brown, probably because of the pres- 
ence of other substances. 

Exp. 26.— Shake together in a test-tube 30 c. c. of water and starch 
of the bulk of a kernel of maize. Add solution of iodine drop by drop, 
agitating until a faint purplish color appears. Pour off half the liquid 



THE VOLATILE PAUT OF PLANTS. 51 

into another test-tube, and add at once to it one-fourth its bulk of 
iodine solution. The latter portion becomes intensely blue by trans- 
mitted, or almost black by reflected, light. On standing, observe that 
in the first case, where starch preponderates, it settles to the bottom, 
leaving a colorless liquid, which shows the insolubility of starch in 
Odd water ; the starch itself has a purple or red tint. In the case 
iodine was used in excess, the deposited starch is blue-black. 

By the prolonged action of dry heat, hot water, acids, 
or alkalies, starch is converted first into amidulio, then 
into dextrin, and finally into the sugars maltose and dex- 
trose, as will be presently noticed. 

Similar transformations are accomplished by the action 
of living yeast, and of the so-called diastase of germinat- 
ing seeds. 

The saliva of man and plant-eating animals likewise 
disintegrates the starch-grains and mostly dissolves the 
starch by converting it into maltose (sugar). It is much 
more promptly converted into sugar by the liquids of the 
large intestine. It is thus digested when eaten by ani- 
mals. Starch is, in fact, one of the most important 
ingredients of the food of man and domestic animals. 

The starch-grains are not homogeneous. After pro- 
longed action of saliva, hot water, or of dilute acids on 
starch -grains, an undissolved residue remains which De- 
Saussure (1819) regarded as nearly related to cellulose. 
This residue is not changed by boiling water, but, under 
prolonged action of dilute acids, it finally dissolves. 
With iodine, after treatment with strong sulphuric acid, 
it gives the blue color characteristic of cellulose. ' There- 
fore it is commonly termed starch-cellulose. 

Starch-cellulose amounts to 0.5 to 6 per cent of the 
starch-grains, varying with the kind of starch and the 
nature and duration of the solvent action. Whether it 
be originally present or a result of the treatment by 
acids, etc., is undecided. 

The chemical composition of starch-cellulose is identi- 
cal with that of the entire starch-grain, viz. : (O 6 H 10 O 5 )n. 

The starch-grains also contain a small proportion of 
amidulin, or soluble starch, presently to be noticed. 



52 HOW CROPS GROW. 



Gelatinous Starch. When starch is heated to near boiling with 12 to 
15 times its weight of water, the grains swell and burst, or exfoliate, 
the water is absorbed, and the whole forms a jelly. This is the starch- 
paste used by the laundress for stiffening muslin. The starch is but 
very slightly dissolved by this treatment. On freezing gelatinous 
starch, the water belonging to it is separated as ice and on melting 
remains for the most part distinct. 

Exp. 27. — Place a bit of starch as large as a grain of wheat in 30 c. c. 
of cold water and heat to boiling. The starch is converted into thin, 
translucent paste. That a portion is dissolved is shown by filtering 
through paper and adding to one-half of the filtrate a few drops of 
iodine solution, when a perfectly clear blue liquid is obtained. The 
delicacy of the reaction is shown by adding to 30 c. c. of water a little 
solution of iodine, and noting that a few drops of the solution of starch 
suffice to make the large mass of liquid perceptibly blue. 

When starch-paste is dried, it forms a hard, horn-like mass. 

Tapioca and Sago are starch, which, from being heated while still 
moist, is partially converted into starch-paste, and, on drying, acquires 
a more or less translucent aspect. Tapioca is obtained from the roots 
of various kinds of Manihot, cultivated in the West Indies and South 
America. Cassava is a preparation of the same starch, roasted. Sago 
is made in the islands of the East Indian Archipelago, from the pith of 
palms (Sagus). It is granulated by forcing the paste through metallic 
sieves. Both tapioca and sago are now imitated from maize starch. 

Next to water and cellulose, starch is the most abund- 
ant ingredient of agricultural plants. 

In the subjoined table are given the proportions of starch in certain 
vegetable products, as determined by Dr. Dragendorff. The quantities 
are, however, somewhat variable. Since the figures below mostly 
refer to air-dry substances, the proportions of hygroscopic water found 
in the plants by Dragendorff are also given, the quantity of which, 
being changeable, must be taken into account in making any strict 
comparisons. 

AMOUXT OF STARCH IX PLAXTS. 

Water. Starch. 

Per cent. Per cent. 

Wheat 13.2 59.5 

Wheat flour 15.8 68.7 

Rye H.O 59.7 

Oats 11.9 46.6 

Barlev 11-5 57.5 

Timothy -seed 12.6 45.0 

Rice (hulled) 13.3 61.7 

Peas 5.0 37.3 

Beans (white) 16.7 33.0 

Clover-seed 10.8 10.8 

Flaxseed 7.6 23.4 

Mustard-seed 8.5 9.9 

Colza-seed 5.8 8.6 

Teltow turnips* dry substance 9.8 

Potatoes dry substance 62.5 



* A sweet and mealy turnip, grown on light soils, for table use. 



THE VOLATILE PART OF PLANTS. 53 

Starch is quantitatively estimated by various methods. 

1. In case of potatoes or cereal grains, it may be determined roughly 
by direct mechanical separation. For this purpose 5 to 20 grams of the 
substance are reduced to fine division by grating (potatoes) or by sof- 
tening in warm water, and crushing in a mortar (grains). The pulp 
thus obtained is washed either upon a fine hair-sieve or in a bag of 
muslin, until the water runs off clear. The starch is allowed to settle, 
is dried, and weighed. The value of this method depends upon the care 
employed in the operations. The amount of starch falls out too low, 
because it is impossible to break open all the minute cells of the sub- 
stance analyzed. 

2. In many cases starch may be estimated with great precision by 
conversion into sugar. For this purpose Sachsse heats 3 grains of air- 
dry substance, contained in a flask with reflux condenser, in a boiling 
water bath for 3 hours, with 200 c. c. of water and 20 c. c. of a 25 per cent 
hydrochloric acid. After cooling, the acid is nearly neutralized with 
sodium hydroxide, and the dextrose into which the starch has been con- 
verted is determined by Allihn's method, described on p. 65. Winton, 
Report Ct. Ag. Exp. St., 1887, p. 132. 

3. For Dragendorff's method, see Henneberg's Journal, fiir Land- 
wirthschaft, 1862, p. 206. 

Amidulin, or Soluble Starch. — A substance soluble 
jn cold water appears to exist in small quantity in the in- 
terior of ordinary starch-grains. It is not extracted by 
cold water from the unbroken starch, as shown by Exp. 
26. On pulverizing starch-grains under cold water by 
rubbing in a mortar with sharp sand, the water, made 
clear by standing or nitration, gives with iodine the char- 
acteristic blue coloration. Exp. 27 shows that when 
starch is gelatinized by hot water, as in making starch 
paste, a small quantity of starch goes into actual solu- 
tion. 

Ordinary insoluble starch may be largely converted 
into soluble starch by moderate heating, either for a long- 
time to the temperature of boiling water or for a short 
space to 375° F. Maschke obtained' a perfectly clear solu- 
tion of potato-starch by heating it with 30 times its bulk 
of water in a sealed glass tube kept immersed for 8 days 
in boiling water. Zulkowski reached the same result by 
heating potato-starch (1 part) with commercial glycerine 
(16 parts). In this case the starch at first swells and 
the mixture acquires a pasty consistence, but, when the 



54 HOW CROPS GROW. 

temperature rises to 375° P., the starch dissolves to a 
nearly clear thin liquid. 

Amidulin also appears to be the first product of the 
action of diastase (the ferment of sprouting seeds) on 
starch and doubtless exists in malt. 

Soluble starch is colored blue by iodine and is thrown 
down from its solution in water, or glycerine, by addition 
of strong alcohol. It redissolves in water or weak alco- 
hol. Its concentrated aqueous solutions gelatinize on 
keeping and the jelly is no longer soluble in water. 
Dilute solutions when evaporated leave a transparent 
residue that is insoluble in water. 

On boiling together diluted sulphuric acid and starch 
the latter shortly dissolves, and if as soon as solution has 
taken place, the acid be neutralized with carbonate of 
lime and removed by filtration, soluble starch remains 
dissolved. (Schulze's Amidulin.) 

Amylodextrin. Nageli has described as Amylodextrin I and Amylo- 
dextrin II, two substances that result from the action of moderately 
strong acids on potato-starch at common temperatures. The starch 
when soaked for many weeks in 12% hydrochloric acid remains nearly 
unchanged in appearance, but the interior parts of the grains grad- 
ually dissolve out, being changed into amylodextrin II, which closely 
resembles and is probably identical with amidulin. 

The starch-grains that remain unchanged in outward appearance, if 
tested with iodine solution from time to time, are at first colored blue, 
but after some days they take on a violet tinge and after prolonged 
action of the acid are made red and finally yellow by iodine. The grains, 
which are now but empty shells, may be freed from acid by washing 
with cold water, and then, if heated to boiling with pure water, they 
readily dissolve to a clear solution (amylodextrin I), from which Nageli, 
by freezing and by evaporation, obtained crystalline disks. These 
bodies, when dry, have the same composition as cellulose, starch, and 
amidulin. 

Dextrin (C 6 H 10 O 5 ) was formerly thought to occur 
dissolved in the sap of all plants. According to Von 
Bibra's investigations, the substance existing in bread- 
grains, which earlier experimenters believed to be dex- 
trin, is for the most part gum. Busse, who examined 
yarious young cereal plants and seeds, and potato tubers, 
for dextrin, found it only in old potatoes and ) T oung 



THE VOLATILE PART OF PLANTS. 55 

wheat plants, and there in very small quantity. Accord- 
ing to Meissl, the soy bean contains 10 per cent of dex- 
trin. 

Dextrin is easily prepared artificially by the trans- 
formation of starch, or, rather, of amidulin derived from 
starch, and its interest to us is chiefly due to this fact. 
When starch is exposed some hours to the heat of an 
oven, or for 30 minutes to the temperature of 415° F., 
the grains swell, burst open, and are gradually converted 
into a light-brown substance, which dissolves readily in 
water, forming a clear, gummy solution. This is dex- 
trin, and thus prepared it is largely used in the arts, 
especially in calico-printing, as a cheap substitute for 
gum arabic. In the baking of bread it is formed from 
the starch of the flour, and often constitutes ten per cent 
of the loaf. The glazing on the crust of bread, or upon 
biscuits that have been steamed, is chiefly due to a coat- 
ing of dextrin. Dextrin is thus an important ingredient 
of those kinds of food which are prepared from the 
starchy grains by cooking. 

Commercial dextrin appears either in translucent 
brown masses or as a yellowish-white powder. On ad- 
dition of cold water, the dextrin readily dissolves, leaving 
behind a portion of unaltered starch. When the solu- 
tion is mixed with strong alcohol, the dextrin separates 
in white flocks. With iodine, solution of commercial 
dextrin gives a fine purplish-red color. 

There are doubtless several distinct dextrins scarcely dis- 
tinguishable except by the different degrees to which they 
affect polarized light or by various chemical deportment 
(reducing effect on alkaline copper solutions). They are 
characterized as erythrodextrins, which give with iodine 
a red color, and achroodextrins, which give no color with 
iodine. Investigators do not agree as to the precise num- 
ber of dextrins that result from the transformation of 
starch. 



56 HOW CROPS GROW. 

Exp. 28.— Cautiously heat a spoonful of powdered starch in a porce- 
lain dish, with constant stirring so that it may not burn, for the space 
of five minutes ; it acquires a yellow, and later, a brown color. Now 
add thrice its bulk of water, and heat nearly to boiling. Observe that 
a slimy solution is formed. Pour it upon a filter ; the liquid that runs 
through contains dextrin. To a portion add twice its bulk of alcohol ; 
dextrin is precipitated. To another portion, add solution of iodine ; 
this shows the presence of dissolved but unaltered starch. To a 
third portion of the filtrate add one drop of strong sulphuric acid and 
boil a few minutes. Test with iodine, which, as soon as all starch is 
transformed, will give a red instead of a blue color. 

Not only heat but likewise acids and ferments produce 
dextrins from starch and, according to some authors, 
from cellulose. In the sprouting of seeds, dextrin is 
abundantly formed from starch and hence is an ingre- 
dient of malt liquors. 

The agencies that convert starch into the dextrins easily 
transform the dextrins into sugars (maltose or dextrose), 
as will be presently noticed. 

The chemical composition of dry dextrin is identical 
with that of dry cellulose, starch, and amidulin. 

Inulin, C3 6 Hg20 36 , closely resembles starch in many 
points, and appears to replace that body in the roots of 
the American artichoke,* elecampane, dahlia, dandelion, 
chicory, and other plants of the same natural family 
(composites). It may be obtained in the form of minute 
white grains, which dissolve easily in hot water, and sep- 
arate again as the water cools. According to Bouchardat, 
the juice of the dahlia tuber, expressed in winter, becomes 
a semi-solid white mass after reposing some hours, from 
the separation of 8 per cent of inulin. 

Inulin, when pure, gives no coloration with iodine. It 
may. be recognized in plants, where it occurs as a solu- 
tion, usually of the consistence of a thin oil, by soaking 
a slice of the plant in strong alcohol. Inulin is insolu- 
ble in this liquid, and under its influence shortly separ- 

* Helianthus tuberosus, commonly known as Jerusalem artichoke, and 
cultivated in Europe under the name topinambowr, ia a native of the 

Northern Mississippi States. 



THE VOLATILE PART OF PLANTS. 57 

ates as a solid in the form of spherical granules, which 
may be identified with the aid of the microscope, and 
have an evident crystalline structure. 

When long heated with water it is slowly but complete- 
ly converted into a kind of sugar (levulose); hot dilute 
acids accomplish the same transformation in a short 
time. It is digested by animals, and doubtless has the 
same value for food as starch. 

In chemical composition, inulin, dried at 212°, differs 
from cellulose and starch by containing for six times 
C 6 H 10 O 5 , the elements of an additional molecule of water ; 
C 3G H 62 36 = 6 C 6 H 10 O 5 + H 2 Kiliani. 

Levulin (C 6 Hi O 5 )n coexists with inulin in the mature 
or frozen tubers of the artichoke, dahlia, etc., and, accord- 
ing to Muentz, is found in unripe rye-grain. It is a highly 
soluble, tasteless, gum-like substance resembling dextrin, 
but without effect on polarized Jight. It appears to be 
formed from inulin when the latter is long heated with 
water at the boiling point, or when the tubers contain- 
ing inulin sprout. Dilute acids readily transform it into 
levulose, as they convert dextrin into dextrose. 

Glycogen (C 6 Hi O 5 )n exists in the blood and mus- 
cles of animals in small quantity, and abundantly in the 
liver, especially soon after hearty eating. It is obtained 
by boiling minced fresh livers with water, or weak potash 
solution, and adding alcohol to the filtered liquid. It is 
a white powder which, with water, makes an opalescent 
solution. It is colored wine-red by iodine. Boiling di- 
lute sulphuric acid converts it into dextrose. With saliva, 
it is said to yield dextrin, maltose and dextrose. Accord- 
ing to late observations, glycogen occurs in the vegetable 
kingdom, having been identified in various fungi and in 
plants of the flax and the potato families. 

The Gums and Pectin Bodies. — A number of 
bodies exist in the vegetable kingdom, which, from the 
similarity of their properties, have received the common 



58 



HOW CROPS GROW. 



designation of gums. The best known are Gum Arabic, 
the gums of the Peach, Cherry and Plum, Gum Traga- 
canth and Bassora Gum, Agar-Agar and the Mucilages 
of various roots, viz., of mallow and comfrey; and of 
certain seeds, as those of flax and quince. 

Gum Arabic exudes from the stems of various species 
of acacia that grow in the tropical countries of the East, 
especially in Arabia and Egypt. It occurs in tear-like, 
transparent, and, in its purest form, colorless masses. 
These dissolve easily in their own weight of water, form- 
ing a viscid liquid, or mucilage, which is employed for 
causing adhesion between surfaces of paper, and for 
thickening colors in calico-printing. 

Gum Arabic is, however, commonly a mixture of at 
least two very similar gums, which are distinguished by 
their opposite effect on polarized light and by the differ- 
ent products which they yield when boiled with dilute 
acids. 

Cherry Gum. — The gum which frequently forms 
glassy masses on the bark of cherry, plum, apricot, peach 
and almond trees, is a mixture in variable proportions of 
two gums, one of which is apparently the same as occurs 
in gum arabic, and is fully dissolved in cold water, while 
the other remains undissolved, but 
swollen to a pasty mass or jelly. 

Gum Tragacanth, which comes 
to us from Persia and Siberia, has 
much similarity in its properties fc^^OOCZDCj 
to the insoluble part of cherry c\ 
gum, as it dissolves but slightly in <% 



water and swells up to a paste or 
jelly. 

The so-called Vegetable m ucilages 
much resemble the insoluble part 
of cherry gum and are found in 
the seeds of flax, quince, lemon, and in various parts of 
many plants. 





Fisr. 13. 



THE VOLATILE PART OF PLANTS. 59 

Flax-seed mucilage is procured by soaking unbroken flaxseed in cold 
water, with frequent agitation, heating the liquid to boiling, strain- 
ing, and evaporating, until addition of alcohol separates tenacious 
threads from it. It is then precipitated by alcohol containing a little 
hydrochloric acid, and washed by the same mixture. On drying, it 
forms a horny, colorless, and friable mass. Fig. 13 represents a highly 
magnified section of the ripe flaxseed. The external cells, a, contain 
the dry mucilage. When soaked in water, the mucilage swells, bursts 
the cells, and exudes. 

The Pectin Bodies. — The flesh of beets, turnips, and 
similar roots, and of most unrij^e fruits, as apples, 
peaches, plums, and berries of various kinds, contain one 
or several bodies which are totally insoluble in water, but 
which, under the action of weak acids or alkaline solu- 
tions, become soluble and yield substances having gummy 
or gelatinous characters, that have been described under 
the names pectin, pectic acid, pectosic acid, metapectic 
acid, etc. Their true composition is, for the most part, 
not positively established. They are, however, closely 
related to the gums. The insoluble substance thus trans- 
formed into gum-like bodies, Fremy termed pectose. 

The gums, as they occur naturally, are mostly mix- 
tures. By boiling with dilute sulphuric or hydrochloric 
acid they are transformed into sugars. 

In the present state of knowledge it appears probable 
that the common gums, for the most part, consist of a 
few chemically distinct bodies, some of which have been 
distinguished more or less explicitly by such names as 
Arabin, Metarabin, Pararabin, Galactin, Paragalactin, 
etc. 

Arabin, or Arabic Acid, is obtained from some va- 
rieties of Gum Arabic* by mixing their aqueous solution 
with acetic acid and alcohol. It is best prepared from 
sugar-beet pulp, out of which the juice has been ex- 
pressed, by heating with milk of lime ; the pulp is 
thereby broken down, and to a large extent dissolves. 



* Those sorts of commercial Gum Arabic which deviate the plane of 
polarization of light to the left contain arabin in largest proportion. 



60 HOW CROPS GROW. 

The liquid, after separating excess of lime and adding 
acetic acid, is mixed with alcohol, whereupon arabin is 
precipitated. Arabin, thus prepared, is a milk-white 
mass which, while still moist, readily dissolves in water 
to a mucilage. It strongly reddens blue litmus and ex- 
pels carbonic acid from carbonates. When dried at 212° 
arabin becomes transparent and has the composition 
Oi 2 H 22 Oii. Dried at 230° it becomes (by loss of a mole- 
cule of "water) Ci 2 H 2 o0 10 , or 2 C 6 H 10 O 5 . 

Arabin forms compounds with various metals. Those 
with an alkali, lime, or magnesia as base are soluble in 
water. Gum arabic, when burned, leaves 3 to 4 per cent 
of ash, chiefly carbonates of potassium, calcium and mag- 
nesium. Arabic acid, obtained by Fremy from beets by 
the foregoing method, but not in a state of purity, was 
described by him as "metapectic acid." To Scheibler 
we owe the proof of its identity with the arabin of gum 
arabic. 

Met arabin. — When arabin is dried and kept at 212° 
for some time, it becomes a transparent mass which is no 
longer freely soluble in water, but in contact therewith 
swells up to a gelatinous mass. This is designated 
metarabin by Scheibler. It is dissolved by alkalies, and 
thus converted into arabates, from which arabin may be 
again obtained. 

The body named parardbin by Reichardt, obtained 
from beet and carrot pulp by treatment with dilute hy- 
drochloric acid, is related to or the same as metarabin. 
Fremy's "pectin," obtained by similar treatment from 
beets, is probably impure metarabin. 

Exp. 34.— Reduce several white turnips or beets to pulp by grating. 
Inclose the pulp in a piece of muslin, and wash by squeezing in water 
until all soluble matters are removed, or until the water comes off 
nearly tasteless. Bring the washed pulp into a glass vessel, with 
enough dilute hydrochloric acid (1 part by bulk of commercial muriatic 
acid to 15 parts of water) to saturate the mass, and let it stand 48 hours. 
Squeeze the acid liquid, filter it, and add alcohol, when " pectin " will 
separate. 



THE VOLATILE PART OF PLANTS. 61 

It may be that metarabin is identical with the "poc- 
tose " of the sugar beet, since both yield arabin under the 
influence of alkalies. It is evident that the composition 
found for dried arabin properly belongs to metarabin, and 
it is probable that arabin consists of metarabin 0i a H sa O u 
plus one or several molecules of water, and that metara- 
bin is an anhydride of arabin. , 

Arabin and metarabin, when heated with dilute sul- 
phuric acid, are converted into a crystallizable sugar 
called arabinose, 5 H 10 O 5 . The gums that exude from 
the stems of cherry, plum and peach trees appear to con- 
sist chiefly of a mixture of freely soluble arabates with 
insoluble metarabin. Gum Tragacanth is perhaps mostly 
metarabin. All these gums yield, by the. action of hot 
dilute acids, the sugar arabinose. 

Galactin, C 6 Hi O 5 , discovered by Muntz in the seeds 
of alfalfa and found in other legumes, has the appearance, 
solubility in water and general properties of arabin, and 
is probably the right-polarizing ingredient of gum arabic. 
Boiled with dilute acids it is converted into the sugar 
galactose, C 6 H 12 6 . 

Paragalactin, C 6 H 10 O5. — In the seeds of the yellow 
lupin exists up to 20 per cent of a body that is insoluble 
in water, but dissolves by warming with alkali solutions, 
and when heated with dilute acids yields galactose. Ac- 
cording to Steiger it probably has the composition C G H 10 O 5 . 
Maxwell has shown it to exist in other leguminous seeds, 
viz., the pea, horse-bean (Faba vulgaris) and vetch. 

In the " Chinese moss," an article of food prepared in 
China from sea-weeds, and in the similar gum agar or 
"vegetable gelatine" of Japan, exists a substance which 
is insoluble in cold water, but with that liquid swells up 
to a bulky jelly, and yields galactose when heated with 
, dilute acids. This corresponds to metarabin. 

Xylin, or Wood Gum. — The wood of many decidu- 
ous trees, the vegetable ivory nut, the cob of Indian 



62 HOW CROPS GROW. 

corn and barley husks, contain 6 to 20 per cent of a sub- 
stance insoluble in cold water, but readily taken up in 
cold solution of caustic soda. On adding to the solution 
an acid, and afterwards alcohol, a bulky white substance 
separates, which may be obtained dry as a white powder 
or a translucent gum-like mass. It dissolves very slightly 
in boiling water, yielding an opalescent solution. The 
composition of this substance was found by Thomsen to 
be C 6 H 10 O 5 . 

Xylin differs from pararabin and pectose in not being 
soluble in milk of lime. It is converted by boiling with 
dilute sulphuric acid into a crystallizable sugar, xylose, 
whose properties have been but little investigated. 

Flax-seed Mucilage, C 6 H 10 O 5 , resembles metarabin, 
but by action of hot dilute acids is resolved into cellulose 
and a gum, which latter is further transformed into dex- 
trose. The yield of cellulose is about four per cent. 

Quince-Seed Mucilage appears to be a compound of 
cellulose and a body like arabin. On boiling with dilute 
sulphuric acid it yields nearly one-third its weight of cel- 
lulose, together with a soluble gum and a sugar, the last 
being a result of the alteration of the gum. The sugar 
is similar to arabinose. 

The Soluble Gums in Bread-grains. — In the bread- 
grains, freely soluble gums occur often in considerable 
proportion. 

TABLE OF THE PROPORTIONS {percent.) OF GUM* IN VARIOUS AIR-DRY 
GRAINS OR MILL PRODUCTS. 

(According to Von Blbra, Die Getr&idearten und das Brod.) 

Wheat kernel 4.50 , Barley flour 6.33 

Wheat flour, superfine 6.25 Barley bran 6.88 

Spelt flour (Triticuin spelta).. 2.48 i Oat meal 3.50 

Wheat bran 8.85 Rice flour 2.00 

Spelt bran 12.52 Millet flour 10.60 

Eye kernel 4.10 Maize meal 3.05 

Rye flour 7.25 j Buckwheat flour 2.85 

Rye bran 10.40 i 



* The " gum " in the above table (which dates from 1859), includes per- 
haps soluble starch and dextrin in some, if not all cases, and, accord- 
ing to O'Sullivan, barley, wheat and rye contain two distinct left-pol- 
arizing gums, which he terms a-amylan and b-amylan. These occur in 
barley to the extent of 2.3 per cent. By action of acids they yield 
dextrose. 



THE VOLATILE PART OF PLANTS. 63 

The experiments of Grouven show that gum arabic is 
digestible by domestic animals. There is little reason to 
doubt that all the gums are digestible and serviceable as 
ingredients of the food of animals. 
• b. The Glucoses, C G Hi 2 6 (or C 5 H 10 O5), are a class of 
sugars having similar or identical composition, but dif- 
fering from each other in solubility, sweetness, melting 
point, crystal-form and action on polarized light. 

The glucoses, with one exception, contain in 100 parts : 

Carbon 40.00 

Hydrogen 6.07 

Oxygen 53.33 

100.00 

Levulose, or Fruit Sugar (Fructose), C 6 H 12 6 , 
exists mixed with other sugars in sweet fruits, honey and 
molasses. Inulin and levulin are converted into this 
sugar by long boiling with dilute acids, or with water 
alone. When pure, it forms colorless crystals, which 
melt at 203°, but is usually obtained as a syrup. Its 
sweetness is equal to that of saccharose. 

Dextrose or Grape Sugar, 6 Hi 2 6 , naturally oc- 
curs associated with levulose in the juices of plants and 
in honey. Granules of dextrose separate from the juice 
of the grape on drying, as may be seen in old " candied " 
raisins. Honey often granulates, or candies, on long 
keeping, from the crystallization of its dextrose. 

Dextrose is formed from starch and dextrin by the ac- 
tion of hot dilute acids, in the same way that levulose is 
produced from inulin. In the pure state it exists as 
minute, colorless crystals, and is, weight for weight, but 
two-thirds as sweet as saccharose or cane-sugar. It fuses 
at 295°. 

Dextrose unites chemically to water. Hydrated glucose, C fi H 12 O 6 Hj , 
occurs in commerce in an impure state as a crystalline mass, which 
becomes doughy at a slightly elevated temperature. This hydrate 
loses its crystal-water at 212°. 

Dissolved in water, dextrose yields a syrup, which is 



64 HOW CROPS GROW. 

thin, and destitute of the ropiness of cane-sugar syrup. 
It does not crystallize (granulate) so readily as cane- 
sugar. 

Exp. 30. — Mix 100 c. c. of water with 30 drops of strong sulphuric acid, 
and heat to vigorous boiling in a glass flask. Stir 10 grains of starch 
with a little water, and pour the mixture into the hot liquid, drop by 
drop, so as not to interrupt the boiling. The starch dissolves, and passes 
successively into amidulin, dextrin, and dextrose. Continue the ebul- 
lition for several hours, replacing the evaporated water from time to 
time. To remove the sulphuric acid, add to the liquid, which may be 
still milky from impurities in the starch, powdered chalk, until the sour 
taste disappears ; filter from the calcium sulphate (gypsum) that is 
formed, and evaporate the solution of dextrose* at a gentle heat to a 
syrupy consistence. On long standing it may crystallize or granulate. 

By this method is prepared the so-called grape-sugar, or starch-sugar 
of commerce, which is added to grape-juice for making a stronger 
wine, and is also employed for preparing syrups and imitating molasses. 
The syrups thus made from starch or corn are known in the trade as 
glucose.^ Imitation-molasses is a mixture of dextrose-syrup with some 
dextrin to make it "ropy." 

Even cellulose is convertible into dextrose by the pro- 
longed action of hot acids. If paper or cotton be first 
dissolved in strong sulphuric acid, and the solution 
diluted with water and boiled, the cellulose is readily 
transformed into dextrose. Sawdust has thus been made 
to yield an impure syrup, suitable for the production of 
alcohol. 

In the formation of dextrose from cellulose, starch, amidulin and 
dextrin, the latter substances take up the elements of water as repre- 
sented by the equation 

Starch, etc. Water. Glucose. 

C 6 H 10 O 5 + H 2 = C 6 H 12 6 

In this process, 90 parts of starch, etc., yield 100 parts of dextrose. 

Trommels Copper test. — A characteristic test for dextrose and levu- 
lose is found in their deportment towards an alkaline solution of cop- 
per, Avhich readily yields up oxygen to these sugars, the copper being 
reduced to yellow cuprous hydroxide or red cuprous oxide. 

Exp. 31.— Prepare the copper test by dissolving together in 30 c. c. of 
warm water a pinch of sulphate of copper and one of tartaric acid ; 
add to the liquid, solution of caustic potash until it acquires a slip- 



* If the boiling has been kept up but an hour or so, the dextrose will 
contain dextrin, as may be ascertained by mixing a small portion of 
the still acid liquid with 5 times its bulk of strong alcohol, which will 
precipitate dextrin, but not dextrose. 

t Under the name, glucose, the three sugars levulose, dextrose and 
maltose were formerly confounded together, by chemists. 



THE VOLATILE PART OF PLANTS. 65 

pery feel. Place in separate test tubes a few drops of solution of cane- 
sugar, a similar amount of the dextrin solution, obtained in Exp. 28; 
of solution of dextrose, from raisins, or from Exp. 30; and of molasses; 
add to each a little of the copper solution, and place them in a vessel 
of hot water. Observe that the saccharose and dextrin suffer little or 
no alteration for a long time, while the dextrose and molasses shortly 
cause the separation of cuprous oxide. 

Exp. 32.— Heat to boiling a little white cane-sugar with 30 c. c. of 
water, and 3 drops of strong sulphuric acid, in a glass or porcelain dish, 
for 15 minutes, supplying the waste of water as needCul, and test the 
liquid as in the last Exp. This treatment transf onus saccharose into 
dextrose and levulose. 

The quantitative estimation of the sugars and of starch is commonly 
based upon the react ion just described. For this purpose the alkaline 
copper solution is made; of a known strength by dissolving a given 
weight of sulphate of copper, etc., in a given volume of water, and the 
dextrose or levulose, or a mixture of both, being likewise made to a 
known volume of solution, the latter is allowed to flow slowly from a 
graduated tube into a measured portion of warm copper solution, until 
the blue color is discharged. Saccharose is first converted into dex- 
trose and levulose, by heating with an acid, and then examined in the 
same manner. 

• Starch is transformed into dextrose by heating with hydrochloric 
acid or warming with saliva. The quantity of sugar stands in definite 
relation to the amount of copper separated, when the experiment is 
carried out under certain conditions. See Allihn, Jour, fur Pr. Chemie, 
XXII, p. 52, 1880. 

Galactose, 6 Hi 2 6 , is formed by treating right- 
polarizing gum arabic, galactin, or milk-sugar with 
dilute acids. It crystallizes, is sweet, melts at 289° and 
with nitric acid yields mucic acid (distinction from ara- 
binose, dextrose and levulose). 

Mannose (Seminose?) C 6 Hi 2 6 is a fermentable sugar 
prepared artificially by oxidation of mannite (see p. 74), 
and, according to E. Fischer, is probably identical with 
the Seminose found by Reiss as a product of the action 
of acids on a body existing in the seeds of coffee and in 
palm nuts. (Beriehte. XXII, p. 365). 

Arabinose, C 5 H 1() 5 , obtained from arabin (of left- 
polarizing gum arabic), and from cherry gum by action 
of hot dilute acids, appears in rhombic crystals. It is 
less sweet than cane sugar, and fuses at 320°. 

c. The Sttcroses, Ci 2 H 22 0ii, are sugars which, boiled with 
dilute acids, undergo chemical change by taking up the 



h ^ 


\J=r. k^ 



66 HOW CROPS GROW. 

elements of water and are thereby resolved into glucoses. 
In this decomposition one molecule of sucrose usually 
yields either two molecules of one glucose or a molecule each 
of two glucoses, C12II22O11 -f- H 2 == C 6 Hi 2 6 -f- C 6 H 12 6 . 

Saccharose, or Cane Sugar, C^H^On, so called 
because first and chiefly prepared from the 
sugar-cane, is the ordinary sugar of com- 
merce. When pure, it is a white solid, 
readily soluble in water, forming a color- Fig. 11 
less, ropy, and intensely sweet solution. It crystallizes 
in rhombic prisms (Fig. 14), which are usually small, as 
in granulated sugar, but in the form of rock-candy may 
be found an inch or more in length. The crystallized 
sugar obtained largely from the sugar-beet, in Europe, 
and that furnished in the United States by the sugar- 
maple and sorghum, when pure, are identical with cane- 
sugar. 

Saccharose also exists in the vernal juices of the wal- 
nut, birch, and other trees. It occurs in the stems of 
unripe maize, in the nectar of flowers, in fresh honey, in 
parsnips, turnips, carrots, parsley, sweet potatoes, in the 
stems and roots of grasses, in the seeds of the pea and 
bean, and in a multitude of fruits. 

Exp. 29. — Heat cautiously a spoonful of white sugar until it melts (at 
356° F.) to a clear yellow liquid. On rapid cooling, it gives a transpar- 
ent mass, known as barley sugar, which is employed in confectionery. 
At a higher heat it turns brown, froths, emits pungent vapors, and be- 
comes burnt sugar, or caramel, which is used for coloring soups, ale, etc. 

The quantity per cent of saccharose in the juice of various plants is 
given in the annexed table. It is, of course, variable, depending upon 
the variety of plant in case of cane, beet, and sorghum, as well as upon 
the stage of growth. 

SACCHAROSE IN PLANTS. 

Per cent. 

Sugar-cane, average 18 Peligot. 

Sugar-beet, " 10 " 

Sorghum 13 Collier. 

Maize, j ust flowered 3| Ludersdorff . 

Sugar-maple, sap, average 2h Liebig. 

Red maple, " " 2J " 



THE VOLATILE PART OF PLANTS. 67 

The composition of saccharose is the same as that of 
arabin, and it contains in 100 parts : 

Carbon 42.11 

1 1 ydrogen r>.4:5 

Oxygen 51.46 

100.00 

Cane-sugar, by long boiling of its concentrated' aqueous 
solution, and under the influence of hot dilute acids (Exp. 
32) and yeast, loses its property of ready crystallization, 
and is converted into levulose and dextrose. 

According to Dubrunf aut, a molecule of cane-sugar takes up the ele- 
ments of a molecule (5.26 per cent.) of water, yielding a mixture of 
equal parts of levulose and dextrose. This change is expressed in 
chemical symbols as follows : 

C 12 H 22 u + H 2 = C 6 H 12 6 + C c H 12 6 
Cane-sugar. Water. Levulose. Dextrose. 

This alterability on heating its solutions occasions a 
loss of one-third to one-half of the saccharose that is 
really contained in cane-juice, when this is evaporated in 
open pans, and is one reason why solid sugar is obtained 
from the sorghum in open-pan evaporation with such dif- 
ficulty. 

Molasses, sorghum syrup, and honey usually contain 
all three of these sugars. 

Honey-dew, that sometimes falls in viscid drops from 
the leaves of the lime and other trees, is essentially a mix- 
ture of the three sugars with some gum. The mannas of 
Syria and Kurdistan are of similar composition. 

Maltose, C12H22O11.H2O, is formed in the sprouting 
of seeds by the action of a ferment, called diastase, on 
starch. It is also prepared by treating starch or glycogen 
with saliva. In either case the starch (or glycogen) takes 
up the elements of water, 2 C 6 H 10 O 5 -f- H 2 = C M HnOn. 
Maltose in crystallizing unites with another molecule of 
water, which it loses at 212°. Maltose, thus dried, 
attracts moisture with great avidity. 

Boiled with dilute acids one molecule of maltose yields 



G8 HOW CROPS GROW. 

two molecules of dextrose, C^H^On -f- H 2 = 2 C 6 Hi 2 6 . 
Maltose is also produced when starch and dextrin are 
heated with dilute acids, and thus appears to be an inter- 
mediate stage of their transformation into dextrose. 

Maltose is accordingly an ingredient of some commer- 
cial "grape-sugars" made from starch by boiling with 
diluted sulphuric acid. 

Lactose, or Milk Sugar, Ci 2 Ho 2 0n -f- H 2 0, is the 
sweet principle of the milk of animals. It is prepared 
for commerce by evaporating whey (milk from which 
casein and fat have been separated for making cheese). 
In a state of purity it forms transparent, colorless crys- 
tals, which crackle under the teeth, and are but slightly 
sweet to the taste. When dissolved to saturation in 
water, it forms a sweet but thin syrup. Heated to 290° 
the crystals become water-free. 

Lactose is said to occur with cane-sugar in the sapo- 
dilla (fruit of Achras sapota) of tropical countries. 
Treatment with dilute sulphuric acid converts it into 
galactose and dextrose. 

C 12 H, 2 O u + H,0 = C fi H 12 O fi + C c H 12 O r , 
Lactose. Water. Galactose. Dextrose. 

Raffinose, Ci 8 H 32 16 + 5 H 2 (?), first discovered 
by Loiseau in beet-sugar molasses, was afterwards found 
by Berthelot in eucalyptus manna, by Lippmann in beet- 
root, and by Boehm & Eitthausen in cotton-seed. It 
crystallizes in fine needles, and is but slightly sweet. It 
begins to melt at 190° with loss of crystal- water, which 
may be completely expelled at 212°. The anhydrous 
sugar fuses at 236°. It is more soluble in water and has 
higher dextrorotatory power than cane-sugar. Heated 
with dilute acids it yields dextrose, levulose and galactose. 

C ls H S2 O ie + 2 H 2 = 3 (C ( .H 12 6 ). 

The Sugars in Bread- Grains. — The older observers 
assumed the presence of dextrose in the bread-grains. 



THE VOLATILE PART OE PLANTS. G9 

Thus, Vauquelin found, or thought he found, 8.5% of 
this sugar in Odessa wheat. More recently, Peligot, 
Mitscherlich, and Stein denied the presence of any sugar 
in these grains. In his work on the Cereals and Bread, 
(Die Getreidearten unci das Brod, 1860, p. 163), Von 
Bibra reinvestigated this question, and found in fresh- 
ground wheat, etc., a sugar having some of the charac- 
ters of saccharose, and others of dextrose and levulose. 
Marcker and Kobus, in 1882, report maltose (which w r as 
unknown to the earlier observers) in sound barley, and 
maltose and dextrose in sprouted barley. 

Von Bibra found in the flour of various grains the following quanti- 
ties of sugar : 

PROPORTIONS OF SUGAR IN AIR-DRY FLOUR, BRAN, AND MEAL. 

Per cent. 

Wheat flour, 2.33 

Spelt flour 1.41 

Wheat bran 4.30 

Spelt bran 2.70 

Bye flour 3.46 

Bye bran 1.86 

Barley meal 3.04 

Barley bran 1.90 

Oat meal 2.19 

Biee flour 0.39 

Millet flour 1.30 

Maize meal 3.71* 

Buckwheat meal 0.91 

Glucosides. — There occur in the vegetable kingdom a 
large number of bodies, usually bitter in taste, which 
contain dextrose, or a similar sugar, chemically combined 
with other substances, or that yield it on decomposition. 
Salicin, from willow bark ; phloridzin, from the bark of 
the apple-tree root ; jalapin, from jalap ; aesculin, from 
the horse-chestnut, and amygdalin, in seeds of almond, 
peach, plum, apple, cherry, and in cherry-laurel leaves, 
are of this kind. The sugar may be obtained from these 
so-called glucosides by heating with dilute acids. 

The seeds of mustard contain the glucoside myronic acid united to 
potassium. This, when the crushed seeds are wet with water, breaks 
up into dextrose, mustard-oil, and acid potassium sulphate, as follows : 
C 10 H 13 K N S, O 10 = C 6 H 12 G -f- C3H3NCS + KHS0 4 

The cambial juice of the conifers contains conif&rin, crystallizing in 



70 HOW CROPS GROW. 

brilliant needles, which yields dextrose and a resin by action of dilute 
acid, and by oxidation produces vanillin, the flavoring principle of the 
vanilla bean. 

Mutual Transformations of the Carthy Urates. — One of 
the most remarkable facts in the history of this group of 
bodies is the facility with which its members undergo 
mutual conversion. Some of these changes have been 
already noticed, but we may appropriately review them 
here. 

a. Transformations in the plant. — In germination, the 
starch which is largely contained in seeds is converted 
into amidulin, dextrin, maltose and dextrose. It thus ac- 
quires solubility, and passes into the embryo to feed the 
young plant. Here these are again solidified as cellulose, 
starch, or other organic principle, yielding, in fact, the 
chief part of the materials for the structure of the seed- 
ling. 

At spring-time, in cold climates, the starch stored up 
over winter in the new wood of many trees, especially the 
maple, appears to be converted into the sugar which is 
found so abundantly in the sap, and this sugar, carried 
upwards to the buds, nourishes the young leaves, and is 
there transformed into cellulose, and into starch again. 

The sugar-beet root, when healthy, yields a juice con- 
taining 10 to 14 per cent, of saccharose, and is destitute 
of starch. Schacht has observed that, in a certain dis- 
eased state of the beet, its sugar is partially converted 
into starch, grains of this substance making their appear- 
ance. (Wilda's Centralblatt, 1863, II, p. 217.) 

In some years the sugar-beet yields a large amount of 
arabin, in others but little. 

The analysis of the cereal grains sometimes reveals the 
presence of dextrin, at others of sugar or gum. 

Thus, Stepf found no dextrin, but both gum and sugar in maize-meal 
{Jour, fur Prakt. Chem., 76, p. 92); while Fresenius, in a more recent 
analysis (Vs. St., I, p. 180), obtained dextrin, but neither sugar nor gum. 
The sample of maize examined by Stepf contained 3.05 p. c. gum and 
3.71 p. c. sugar; that analyzed by Fresenius yielded 2.33 p. c. dextrin. 



THE VOLATILE PART OF PLANTS. 71 

Marcker & Kobus made comparative analyses of well-cured and of 
sprouted barley, with the following results per cent : 

Sound. Grown. 

Starch 64.10 57.98 

Soluble starch 1.76 1.17 

Dextrin 1.10 0.00 

Dextrose 0.00 4.92 

Maltose 3.12 7.92 

The various gums are a result of the transformation of 
cellulose, as Mohl first showed by microscopic study. 

b. In the animal, the substances we have been describ- 
ing also suffer transformation when employed as food. 
During the process of digestion, cellulose, so far as it is 
acted upon, starch, dextrin, and probably the gums, are 
all converted into dextrose or other sugars, and from 
these, in the liver especially, glycogen is formed. 

c. Many of these changes may also be produced apart 
from physiological agency, by the action of heat, acids, 
and ferments, operating singly or jointly. 

Cellulose and starch are converted, by boiling with a 
dilute acid, into amidulin, dextrin, maltose and dextrose. 
Cellulose and starch acted upon for some time by strong 
nitric acid give compounds from which dextrin^may be 
separated. Cellulose nitrate sometimes yields gum (dex- 
trin) by its spontaneous decomposition. A kind of gum 
also appears in solutions of cane-sugar or in beet-juice, 
when they ferment under certain conditions. Inulin and 
the gums yield glucoses, but no dextrin, when boiled 
with weak acids. 

d. It will be noticed that while physical and chemical 
agencies produce these metamorphoses mostly in one di- 
rection, under the influence of life they go on in either 
direction. 

In the laboratory we can in general only reduce from a 
higher, organized, or more complex constitution to a 
lower and simpler one. In the vegetable, however, all 
these changes, take place with the greatest facility. 

The Chemical Composition of the Carlhydrates. — It 



TZ now crops grow. 

has already appeared that the substances just described 
stand very closely related to each other in chemical com- 
position. In the following table their composition is ex- 
pressed in formulae. 

CHEMICAL FORMULAE OF THE CARBHYDKATES. 



Amyloses. 






Dried 


Cellulose, 






C Hxo O s 


Soluble cellulose, 






}C' 6 K 10 O 6 * 


Amyloid, 






Starch, 






C 6 H 10 5 


Soluble starch, 






) 


Amidulin, 






j C 6 H w 0, * 


Amylodextrin, 






) 


Dextrin, 






G 6 H ]0 5 


Inulin, 


6 (C 6 H 10 5 ) + H 2 O : 




C36 Hfi2 O 31 


Levulin, 


2 (C 6 H 10 5 ) + H, : 




l~>12 "22 ^-'11 


Glycogen, 






G 6 H 10 G 5 


Pectin, 






(?) 


Arabin, ) 
Metarabin, ] 


2 (C 6 H 10 5 ) + H 2 




C12 H 22 O n 


Galactin, 






C 6 H 10 5 


Paragalactin, 






C 6 H ]0 G 5 


Flax-seed mucilage, 






C H 10 5 


Quince-seed mucilage, 


^6 Hio Os + 2 (C 6 H 10 


5 )-H 2 = 


Gis H 28 14 


Glucoses. 


Crystallized 






Levulose, 


Co H 12 O g 


• 


C 6 H 12 Go 


Dextrose, 


C 6 H M 7 and C 6 H 12 


o G 


Co H 12 Go 


Galactose, 


C fi H 12 O e ' 




C„ H ]2 G 6 


Mannose, 


C 6 Hm 6 




C 6 H ls O fi 


Arabinose, 


C 5 H 10 6 




C 5 H 10 0,3 


Sucr oses. 








Saccharose, 


C 12 H;J2 U 




C 12 H 22 ()„ 


Maltose, 


C 12 H^ 12 




C 12 H 22 O n 


Lactose, 


C12 "2A "l2 




G12 H 22 O u 


Raffinose, 


Cl8 "40 2 i 




Gis H 32 16 



As above formulated, it is seen that all these bodies, 
except arabinose, contain 6 atoms of carbon, or a num- 
ber which is some simple multiple of 6, united to as much 
hydrogen and oxygen as form in most cases 5, 6 or 11 
molecules of water (H 2 0). Being thus composed of car- 
bon and the elements of water they are termed Carbhy- 
drates. 

The mutual convertibility of the carbhydrates is the 



* These soluble bodies when dried probably lose water which is 
essential to their composition, as on drying they become insoluble. 



THE VOLATILE PART OF PLANTS. 73 

easier to understand since it takes place by the loss or 
gain of several molecules of water. 

The formulae given are the simplest that accord with 
the results of analysis. In case of many of the amyloses 
it is probable that the above formulae should be multi- 
plied by 2, 4, or 6, or even more, in order to reach the 
true molecular weight. 

Isomerism.— Bodies which — like cellulose and dextrin, or like levu- 
lose and dextrose— are identical in composition, and yet are character- 
ized by different properties and modes of occurrence, are termed isom- 
eric; they are examples of isomerism. These words are of Greek deri- 
vation, and signify of equal measure. 

We must suppose that the particles of isomeric bodies which are com- 
posed of the same kinds of matter, and in the same cpiantities, exist in 
different states of arrangement. The mason can build, from a given 
number of bricks and a certain amount of mortar, a simple wall, an 
aqueduct, a bridge or a castle. The composition of these unlike struc- 
tures may be the same, both in kind and quantity; but the structures 
themselves differ immensely, from the fact of the diverse arrangement 
of their materials. In the same manner we may suppose starch to dif- 
fer from dextrin by a difference in the relative positions of the atoms 
of carbon, hydrogen, and oxygen in the molecules which compose 
them. 

By use of "structural formulae " it is sought to represent the different 
arrangement of atoms in the molecules of isomeric bodies. In case 
of substances so complex as the sugars, attempts of this kind have but 
recently met with success. The following formulae exhibit to the 
chemist the probable differences of constitution between dextrose and 
levulose. 

Dextrose. Levulose. 

H H 

H-C-0 H H-C-0 H 

H— C— O H C— O 

C— H H— C— O H 

H— C— O H H C— O H 

O H— C— O H H C— O 
C— O H H C— O 



H 

H 



H 



To those familiar with advanced Organic Chemistry the foregoing 
formula 1 , to some extent, "account for" the chemical characters of 
these sugars, and explain the different products which they yield 
under decomposing influences. 

APPENDIX TO THE CARBHYDRATES. 

Nearly related to the Carbhydrates are the following substances:— 



74 HOW CROPS GROW. 



Mannite, C 6 H u 6 , is abundant in the so-called manna of the apoth- 
ecary which exudes from the bark of several species of ash that 
grow in the eastern hemisphere (Fraxinus ornus and rotund i/olia). It 
likewise exists in the sap of our fruit trees, in edible mushrooms, and 
sometimes is formed in the fermentation of sugar (viscous fermenta- 
tion), it appears in minute colorless crystals and has a sweetish taste. 
It may be obtained from dextrose and levulose by the action of 
nascent hydrogen as liberated from sodium amalgam and water, 
CaH u 6 + H, = C 6 H 14 6 . 

Dulcite, C G H u 6 , is a crystalline substance found in the common cow- 
wheat (Melampyrum nemorosum) and in Madagascar manna. It is 
obtained from milk-sugar by the action of sodium amalgam. 

The isomeres mannite and dulcite, when acted on by nitric acid, are 
converted into acids which are also isomeric. Mannite yields saccharic 
acid, which is also formed by treating cane-sugar, dextrose, levulose, 
dextrin and starch with nitric acid. Dulcite yields, by the same treat- 
ment, mucic acid, which is likewise obtained from arabin and other 
gums. Milk-sugar yields both saccharic and mucic acid. Saccharic 
acid is very soluble in water. Mucic acid is quite insoluble. Both 
have the formula C 6 H 10 O 8 . 

The Pectin-bodies. The juice of many ripe fruits, when mixed with 
alcohol, yields a jelly-like precipitate which has long been known 
under the name of pectin. When the firm flesh of acid winter-fruits is 
subjected to heat, as in baking or stewing, it sooner or later softens, 
becomes soluble in water and yields a gummy liquid from which by 
adding alcohol the same or a similar gelatinous substance is separated. 
Fremy supposes that in the pulp " pectose " exists which is transformed 
by acids and heat into pectin. 

Exp. 33.— Express, and, if turbid, filter through muslin the juice of a 
ripe apple, pear, or peach. Add to the clear liquid its own bulk of 
alcohol. Pectin is precipitated as a stringy, gelatinous mass, which, 
on drying, shrinks greatly in bulk, and forms, if pure, a white sub- 
stance that may be easily reduced to powder, and is readily soluble in 
cold water. 

Pectosic and Pectlc Acids.. These bodies, according to Fremy, com- 
pose the well-known fruit-jellies. They are both insoluble or nearly 
so in cold water, and remain suspended in it as a gelatinous mass. 
Pectosic acid is soluble in hot water, and is supposed to exist in those 
fruit-jellies which liquefy on heating but gelatinize on cooling. Pec- 
tic acid is stated to be insoluble in hot water. According to Fremy, 
pectin is changed into pectosic and pectic acids and finally into meta- 
pectic acid by the action of heat and during the ripening process. 

Exp. 35.— Stew a handful of sound cranberries, covered with water, 
just long enough to make them soft. Observe the speedy solution of 
the firm pulp or "pectose." Strain through muslin. The juice contains 
soluble pectin, which may be precipitated from a small portion by 
alcohol. Keep the remaining juice heated to near the boiling point in 
a water bath (i. e., by immersing the vessel containing it in a larger 
one of boiling water). After a time, which is variable according to 
the condition of the fruit, and must be ascertained by trial, the juice 
on cooling or standing solidifies to a jelly, that dissolves on warming, 
and reappears again on cooling— Fremy's pectosic acid. By further 



THE VOLATILE PART OF PLANTS. 



75 



heating, the juice may form a jelly which is permanent when hot— 
pectic acid. 

Other ripe fruits, as quinces, strawberries, peaches, grapes, apples, 
etc., may be employed for this experiment, but in any case the time 
required for the juice to run through these changes cannot be pre- 
dicted safely, and the student may easily fail in attempting to fol- 
low them. 

Scheibler having shown that Fremy's metapectic acid of beets is 
arabic acid, it is probable that Fremy's pectin, peetic acid and pectosic 
acid of fruits, are bodies similar to or identical with the gums already 
described. The pectin bodies of fruits have not yet been certainly ob- 
tained in a state of purity, since the analyses of preparations by vari- 
ous chemists do not closely agree. 

The Vegetable Acids. — Nearly every family of the 
vegetable kingdom, so far as investigated, contains one 
or more organic acids peculiar to itself. Those of more 
general occurrence which alone concern us here are few 
in number and must be noticed very concisely. 

The vegetable acids rarely occur in plants in the free 
state, but are for the most part united to metals or 
to organic bases in the form of salts. The vegetable 
acids consist of carboxyl, COOH, united generally to 
a hydrocarbon group.. They are monobasic, dibasic or 
tribasic, according as they contain one, two or three 
carboxyls. • 

The Monobasic Acids, to be mentioned here, fall into 
two groups, viz. : Fatty acids and Oxyfatty acids. 

The Fatty Acids constitute a remarkable "homolo- 
gous series, " the names and formulae of a number of 
which are here given : 



Formic 

Acetic 

Propionic 

Butyric 

Valeric 

Caproic 

Oenanthylic 

Caprylic 

Pelargonic 

Capric 

Umbelllc 

Laurie 

Tridecylic 



acid, H, C O O H 
" CH,COOH 
" C 2 H 5 COOH 
" C 3 H 7 C00H 
" C 4 H 9 C0 0H 
" C 5 H n COOH 
C 6 H,g COOH 
C 7 H 13 COOH 
C 8 H 17 C O O H 
C„ II,, C OOH 
C M Ha COOH 
C u H 23 COOH 
Ci, H 25 COOH 



Found in 
Pine needles, red ants, guano. 
Vinegar and many vegetable juices. 
Yarrow-flowers. 

Butter,limburger cheese, parsnip seeds. 
Valerian root, old cheese. 
Butter, cocoanut oil. 
(Artificial.) [fusel oil. 

Butter, cocoanut oil, limburger cheese, 
Rose-geranium. 
Butter, cocoanut oil. 
Seeds of California laurel. 
Laurel oil, butter, bayberry tallow. 
(Artificial.) 



76 



HOW CROPS GROW. 



Myristic acid,C 13 H 27 COOH 


Nutmeg oil. 


Isocetic 


u 


C H H ffl COOH 


Seeds of Jatropha. 


Palmitic 


it 


C 15 H 31 C H 


Butter, tallow, lard, palm oil. 


Margaric 


" 


C 16 H33 C H 


(Artificial.) 


Stearic 


M 


C 17 Hgg C O H 


Tallow, lard. 


Nonclecylic 


" 


C 18 H 37 C O H 


(Unknown.) 


Arachic 


u 


C 19 H 39 COOH 


Butter, peanut oil. 


Medullic 


II 


C, H 41 C O H 


Marrow of ox. 


Behenic 


'1 


C 21 H 43 C O H 


Oil of Moringa oleif era. 






C 2 , H 45 C H 

C M H 47 COOH 


(Unknown.) 
Beech-wood tar. 


Lignoceric 


u 


Hyenic 


" 


C 4 H 49 C H 


Hyena-fat. 






C.^ H 51 C H 


(Unknown.) 




Cerotic 


u 


C^ H 53 C H 


BeesAvax, carnauba wax, wool-fat, 



It is to be observed that these fatty acids make a nearly 
complete series, the first of which contains one carbon 
and two hydrogen atoms, and the last 27 carbon and 54 
hydrogen atoms, and that each of the intermediate acids 
differs from its neighbors by CH 2 . The first two acids 
in this series are thin, intensely sour, odorous liquids 
that mix with water in all proportions ; the third to the 
ninth inclusive are oily liquids whose consistency in- 
creases and whose sourness and solubility in water dimin- 
ish with their greater carbon content. The tenth and 
other acids are at common temperatures nearly tasteless, 
odorless, and fatty solids, which easily melt to oily liquids 
whose acid properties are but feebly manifest. Of these 
acids a few only require further notice. 

Acetic Acid, C 2 H 4 2 , or CH 3 COOH, formed in the 
"acetic fermentation" from cider, malt, wine and whis- 
ky, alcohol being in each case its immediate source, 
exists free in vinegar to the extent of about 5 per cent. 
When pure, it is a strongly acid liquid, blistering the 
tongue, boiling at 246°, and solidifying at about 60° to a 
white crystalline mass. In plants, acetic acid is said to 
exist in small proportion, mostly as acetate of potassium. 

Butyric Acid, C 4 H 8 2 , or CH 8 CH 2 CH 2 COOH, in the 
free state, occurs in rancid butter, whose disagreeable 
odor is largely due to its presence. In sweet butter it 
exists only as a glyceride or fat of agreeable qualities. 



THE VOLATILE PART OF PLANTS. 77 

The other acids of this series are mostly found in veg- 
etable and animal fats or fatty oils. (See p. 85.) 

Oxyfatty Acids. — The acids of this class differ from 
the corresponding fatty acids by having an additional 
atom of oxygen, or by the substitution of OH for H in 
the latter. There are two acids of this class that may be 
briefly noticed, viz. : oxyacetic, or glycollic acid, and oxy-, 
propionic or lactic acid. ' 

Glycollic Acid, C 2 H 4 3 or HOCH 2 COOH, exists in 
the juices of plants (grape-vine), and like acetic acid may 
be formed by oxidizing alcohol. 

Lactic, C 3 H 6 3 , or CH 3 CH (OH) COOH, is the acid 
that is formed in the souring of milk, where it is produced 
from the milk-sugar by a special organized ferment. It 
is also formed in the "lactic fermentation" of cane- 
sugar, starch and gum, and exists accordingly in sour- 
kraut and ensilage. 

The fatty and oxyfatty acids are monobasic, i.e., they 
contain one carboxyl, COOH, and each acid forms one 
salt only, with potassium, for instance, in which the hy- 
drogen of the carboxyl is replaced by the metal. Thus, 
potassium acetate is CH 3 COOK. 

The oxyfatty acids are especially prone to form anhy- 
drides by loss of the elements of water. Lactic acid 
cannot be obtained free from admixed water when its 
aqueous solutions are evaporated, without being partially 
converted into an anhydride. Gentle heat up to 270° 
changes it, with loss of water, into so-called lactolactic 
acid,* C 6 H 10 O 5 . a solid, scarcely soluble in water, but that 
slowly reproduces lactic acid by contact with water, and 
dissolves in alkalies to form ordinary lactates. Lacto- 
lactic acid, heated to 290°, loses water with formation 
of lactide,\ C 6 H 8 4 , a solid nearly insoluble in water, but 
also convertible into lactic acid by water, and into lactates 
by alkalies. 

~2 (C 3 H 6 3 ) = C 6 H 10 O 5 + H 2 t C 6 H 10 O 5 = C 6 H 8 4 + H 2 < > 



/8 HOW CROPS GROW. 



Dibasic Acids. 


— The acids of this 


class 


requiring notice 


are 












Oxalic acid- 






C 2 H 2 4 , or 




COOH 
COOH 


Malonic acid, 






C 3 H 4 4 , or 




rTT /COOH 
tM 2 \C00H 


Succinic acid, C 4 H 6 4 , or 
Malic acid (Oxijsuccinic acid), C 4 H 6 5 , or 

Tartaric acid (Dioxysuccinic C 4 H 6 6 , or 

acid), 




CH 2 — COOH 

CH 2 — COOH 
CHo— COOH 

CH(OH)— COOH 
CH(OH) COOH 

CH(OH) COOH 




The salts formed by union of these acids with metallic 
bases are either primary or secondary, according as the 
metal enters into one or two of the carboxyls. 

Oxalic acid, C 2 H 2 4 , exists largely in the common 
sorrel, and is found in greater or less 
quantity in nearly all plants. The pure 
acid presents itself in the form of color- 
less, brilliant, transparent crystals, not 
unlike Epsom salts in appearance (Fig. Fig. 15. 

15), but having an intensely sour taste. 

Primary potassium oxalate (formerly termed acid ox- 
alate of potash), HOOC— COOK, occasions the sour taste 
of the juice of sorrel, from which it may be obtained 
in crystals by evaporating off the water. It may also be 
prepared by dissolving oxalic acid in water, dividing the 
solution into two equal parts, neutralizing * one of these 
by adding solution of potash and then mixing the two 
solutions and evaporating until crystals form. 

Secondary potassium oxalate (neutral oxalate of potash), 
KOOC — COOK, is the result of fully neutralizing oxalr 
acid with potash solution. It has no sour taste. 

Primary calcium oxalate exists dissolved in the cc. 
of plants so long as they are in active growth. Second- 
ary calcium oxalate is extremely insoluble in water, and 

* As described in Exp. 38. 



THE VOLATILE PART OF PLANTS. 79 

very frequently occurs within the plant as microscopic 
crystals. These are found in large quantity in the ma- 
ture leaves and roots of the beet, in the root of garden 
rhubarb, and especially in many lichens. 

Secondary ammonium oxalate is employed as a test for 
calcium. 

Exp. 36.— Dissolve 5 grams of oxalic acid in 50 c. c. of hot water, add 
solution of ammonia or solid carbonate of ammonium until the odor of 
the latter slightly prevails, and allow the liquid to cool slowly. Long, 
needle-like crystals of ammonium oxidate separate on cooling, the 
compound heing sparingly soluble in cold water. Preserve for future 
use. 

Exp. 37.— Add to any solution of lime, as lime-water (see note, p. 20), 
or hard well-water, a few drops of solution of ammonium oxalate. 
Secondary Calcium oxalate immediately appears as a white, powdery 
precipitate, which, from its extreme insolubility, serves to indicate the 
presence of the minutest quantities of lime. Add a few drops of hydro- 
chloric or nitric acid to the calcium oxalate; it disappears.. Hence 
ammonium oxalate is a test for lime only in solutions containing no free 
mineral acid. (Acetic and oxalic acids, however, have little effect upon 
the test.) 

Malonic acid and Succinic acid occur in plants in 
but small quantities. The former has been found in 
sugar-beets, the latter in lettuce and unripe grapes. 

Malic acid, C 4 H 6 5 , is the chief sour principle of ap- 
ples, currants, gooseberries, plums, cherries, strawberries, 
and most common fruits. It exists in small quantity in a 
multitude of plants. It is found abundantly in the gar- 
den rhubarb, and primary potassium malate maybe ob- 
tained in crystals by simply evaporating the juice of the 
leaf-stalks of this plant. It is likewise abundant as cal- 
cium salt in the nearly ripe berries of the mountain ash, 
and in barberries. Calcium malate also occurs in con- 
siderable quantity in the leaves of tobacco, and is often 
encountered in the manufacture of maple sugar, separat- 
ing as a white or gray sandy powder during the evapora- 
tion of the sap. 

Pure malic acid is only seen in the chemical laboratory, 
and presents white, crystalline masses of an intensely 
sour taste. It is extremely soluble in water. 




80 HOW CROPS GROW. 

Tartaric acid, C 4 H 6 O c , is abundant in the grape, 
from the juice of which, during fermentation, it is de- 
posited as argol. This, on purification, 
yields the cream of tartar (bitartrate of 
potash) of commerce. Tartrates of po- 
tassium and calcium exist in small quan- 
tities in tamarinds, in the unripe berries Fi s- 16 » 
of the mountain ash, in the berries of the sumach, in cu- 
cumbers, potatoes, pineapples, and many other fruits. 
The acid itself may be obtained in large glassy crystals 
(see Fig. 16), which are very sour to the taste. 

Of the Tribasic Acids known to occur in plants, but 
one need be noticed here, viz., citric acid. 

c h 2 c o o H 

C 6 H 8 7 , or C (O H) C O O H 

CH,COOH 

Citric acid exists in the free state in the juice of the 
lemon, and in unripe tomatoes. It accompanies malic 
acid in the currant, gooseberry, cherry, strawberry, and 
raspberry. It is found in small quantity in tobacco 
leaves, in the tubers of the artichoke (Helianthus) , in the 
bulbs of onions, in beet-roots, in coifee-berries, in seeds of 
lupin, vetch, the pea and bean, and in the needles of the 
fir tree, mostly as potassium or calcium salt. It also 
exists in cows' milk. 

In the pure state, citric acid forms large transparent or 
white crystals, very sour to the taste. 

Relations of the Vegetable Acids to each other, and to the Amyloses — 
Oxalic, malic, tartaric and citric acids usually occur together in our 
ordinary fruits, and some of them undergo mutual conversion in the 
living plant. 

According to Liebig, the unripe berries of the mountain ash contain 
much tartaric acid, which, as the fruit ripens, is converted into malic 
acid. Tartaric acid can be artificially transformed into malic acid, and 
this into succinic acid. 

"When citric, malic and tartaric acids are boiled with nitric acid, or 
heated with caustic potash, they all yield oxalic acid. 

Cellulose, starch, dextrin, the sugars, yield oxalic acid when heated 



THE VOLATILE PART OF PLANTS. 81 

with potash or nitric acid. Commercial oxalic acid is thus made from 
sawdust. 

Gum (Arabic), sugar and starch yield tartaric acid by the action of 
nitric acid. 

Definition of Acids, Bases, and Salts. — In the popular 
sense, au acid is any body having a sour taste. It is, in 
fact, true that all sour substances are acids, but all acids 
are not sour, some being tasteless, others bitter, and some 
sweet. A better characteristic of an acid is its capability 
of forming salts by its interaction with bases. The strong- 
est acids, i. e., those bodies whose acid characters are most 
highly developed, if soluble, so as to have any effect on 
the nerves of taste, are sour, viz., sulphuric acid, phos- 
phoric acid, nitric acid, etc. 

Bases are the opposite of acids. The strongest bases, 
when soluble, are bitter and biting to the taste, and cor- 
rode the skin. Potash, soda, lime, and ammonia are ex- 
amples. Magnesia, oxide of iron, and many other com- 
pounds of metals with oxygen, are insoluble bases, and 
hence destitute of taste. Potash, soda, and ammonia 
are termed alkalies ; lime and magnesia, alkali-earths. 

Salts are compounds that result from the mutual ac- 
tion of acids and bases. Thus, in Exp. 20, the salt, cal- 
cium phosphate, was produced by bringing together 
phosphoric acid, and the base, lime. In Exp. 37, cal- 
cium oxalate was made in a similar manner. Common 
salt — in chemical language, sodium chloride — is formed 
when caustic soda is mixed with hydrochloric acid, water 
being, in this case, produced at the same time. 

NaOH + HCl = NaCl -f H 2 

Sodium hydroxide. Hydrochloric acid. Sodium chloride. Water. 

In general, salts having a metallic base are formed by 
substituting the metal for the hydrogen of the acid ; or if 
an organic acid, for the hydrogen that is united to oxy- 
gen, i.e., of carboxyl, COOH. 

Ammonia, NH 3 , and many organic bases unite directly 
to acids in forming salts. 



NH 3 


+ 


HC1 


Ammonia. 




Hydrochloric acid, 


NH, 


+ 


CH3COOH 


Ammonia. 




Acetic acid. 



82 HOW CHOPS GROW. 

NH^Cl 

Ammonium chloride.* 

CH 3 COONH< 
Ammonium Acetate. 

Test for acids and alkalies.— Many vegetable colors are altered by sol- 
uble acicls or soluble bases (alkalies), in such a manner as to answer the 
purpose of distinguishing these two classes of bodies. A solution of 
cochineal may be employed. It has a ruby-red color when concen- 
trated, but, on mixing with much pure water, becomes orange or yel- 
lowish-orange. Acids do not affect this color, while alkalies turn it to 
an intense carmine or violet-carmine, which is restored to orange by 
acids. 

Exp. 38.— Prepare tincture t of cochineal by pulverizing 3 grams of 
cochineal, and shaking frequently with a mixture of 50 c. c. of strong 
alcohol and 200 c. c. of water. After a day or two, pour off the clear 
liquid for use. 

To a cup of water add a few drops of strong sulphuric acid, and to an- 
other similar quantity add as many drops of ammonia. To these liquids 
add separately 5 drops of cochineal tincture, observing the coloration 
in each case. Divide the dilute ammonia into two portions, and pour 
into one of them the dilute acid, until the carmine color just passes into 
orange. Should excess of acid have been incautiously used, add am- 
monia, until the carmine reappears, and destroy it again by new por- 
tions of acid, added dropwise. The acid and base Satis neutralize each 
other, and the solution contains sulphate of ammonia, but no free acid 
or base. It will be found that the orange-cochineal indicates very mi- 
nute quantities of ammonia, and the carmine-cochineal correspond- 
ingly small quantities of acid. 

In the formation of salts, the acids and bases more or 
less neutralize each other's properties, and their com- 
pounds, when soluble, have a less sour or less acrid taste, 
and act less vigorously on vegetable colors than the acids 
or bases themselves. Some soluble salts have no taste 
at all resembling either their base or acid, and have 
no eifecfc on vegetable colors. This is true of common 
salt, glauber salts or sulphate of sodium, and saltpeter or 
nitrate of potassium. Others exhibit the properties of their 
base, though in a reduced degree. Carbonate of am- 
monium, for example, has much of the odor, taste, and 



* Also termed amnionic chloride, ammonia hydrochlorate, ammonia 
hydrochloride, and formerly muriate of ammonia. 

t Tinctures, in the language of the apothecary, are alcoholic solutions. 
Tincture of litmus (procurable of the apothecary), or of dried red cab- 
bage, may also be employed. Litmus is made red by soluble acids, and 
blue by soluble bases. With red cabbage, acids develop a purple, and 
the bases a green color. 



THE VOLATILE PART OF PLANTS. 



83 



effect on vegetable colors that belong to ammonia. Car- 
bonate of sodium has the taste and other properties of caus- 
tic soda in a greatly mitigated form. On the other hand, 
sulphates of aluminum, iron, and copper, have slightly 
acid characters. 

5. Fats and Oils (Wax). — AYe have only space here 
to notice this important class of bodies in a very general 
manner. In all plants and nearly all parts of plants we 
find some representatives of this group ; but it is chiefly 
in certain seeds that they occur most abundantly. Thus 
the seeds of hemp, flax, colza, cotton, bayberry, peanut, 
butternut, beech, hickory, almond, sunflower, etc., con- 
tain 10 to 70 per cent of oil, which may be in great part 
removed by pressure. In some plants, as the common 
bayberry and the tallow-tree of Nicaragua, the fat is 
solid at ordinary temperatures, and must be extracted by 
aid of heat ; while, in most cases, the fatty matter is 
liquid. The cereal grains, especially oats and maize, con- 
tain oil in appreciable quantity. The mode of occur- 
rence of oil in plants is shown in Fig. 17, which repre- 
sents a highly magnified section of the flax-seed. The 
Oil exists as minute, transparent globules in the cells, /. 
From these seeds the oil may be completely extracted by 

ether, benzine, or sulphide of car- 
bon, which dissolve all fats with 
readiness, but scarcely affect the 
other vegetable principles. 

Many plants yield small quanti- 
ties of wax, which often gives a 
d —J^JC^^JC^C gl° ss y coat to their leaves, or 
n^^y^^^^^y forms a bloom upon their fruit. 

The lower leaves of the oat-plant 
at the time of blossom contain, in 
the dry state, 10 per cent of fat 
Fl £- 17, and wax (Arendt). Scarcely two 

of these oils, fats, or kinds of wax, are exactly alike in 




ooooa 



84 HOW CROPS GROW. 

their properties. They differ more or less in taste, odor, 
and consistency, as well as in their chemical composition. 
The "oils" are the simplest in chemical composition, 
and have the lowest melting points. The "fats" have 
larger content of carbon, and higher points of fusion. 
The varieties of wax are most complex in composition, 
and have the highest melting points and greatest content 
of carbon. These differences are mostly gradational. In 
chemical constitution these bodies are alike. 

Exp. 39.— Place a handful of fine and fresh corn or oatmeal, which has 
been dried for an hour or so at a heat not exceeding 212°, in a bottle. 
Pour on twice its bulk of ether, cork tightly, and agitate frequently for 
half an hour. Dram off the liquid (filter, if need be) into a clean porce- 
lain dish, and allow the ether to evaporate. A yellowish oil remains, 
which, by gently warming for some time, loses the smell of ether and 
becomes quite pure. 

The fatty oils must not be confounded with the ethe- 
real, essential, or volatile oils, which, however, do not occur 
to much extent in agricultural plants. The former can 
not evaporate except at a high temperature, and when 
brought upon paper leave a permanent "grease spot." 
The latter readily volatilize, leaving no trace of their 
presence. The former, when pure, are without smell or 
taste. The latter usually possess marked odors, which 
adapt many of them to use as perfumes. 

In the animal body, fat (in some insects, wax) is formed 
or appropriated from the food, and accumulates in con- 
siderable quantities. How to feed an animal so as to 
cause the most rapid and economical fattening is one of 
the most important questions of agricultural chemistry. 

However greatly the various fats may differ in external 
characters, they are all mixtures of a few elementary fats. 
The most abundant and commonly-occurring fats, espe- 
cially those which are ingredients of the food of man and 
domestic animals — e.g., tallow, olive oil, and butter — con- 
sist mainly of three substances, which we may briefly 
notice. These elementary fats are Stearin, Palmiiin, 



THE VOLATILE PART OF PLANTS. 85 

and Olein* and they consist of carbon, oxygen, and hy- 
drogen, the first-named element being greatly prepon- 
derant. 

Stearin is represented by the formula O 57 H 110 O6. It 
is the most abundant ingredient of the common fats, and 
exists in largest proportion in the harder kinds of tallow. 

Exp. 40.— Heat mutton or beef tallow in a bottle that may be tightly 
corked, with ten times its bulk of concentrated ether, until a clear 
solution is obtained. Let cool slowly, when stearin will crystallize out 
in pearly scales. 

Palmitin, C 5 iH 98 6 , receives its name from the palm 
oil, of Africa, in which it is a large ingredient. It forms 
a good part of butter, and is one of the chief constituents 
of beeswax, and of bay berry tallow. 

Olein, C 5 7H 10 4O 6 , is the liquid ingredient of fats, 
and occurs most abundantly in the oils. It is prepared 
from olive oil by cooling down to the freezing point, 
when the stearin and the palmitin solidify, leaving the 
o!ein still in the liquid state. 

Other elementary fats, viz., butyrin, laurin, myristin, etc., occur in 
small quantity in butter, and in various vegetable oils. Flaxseed oil 
contains linolein ; castor oil, ricinolein, etc. 

We have already given the formulae of the principal 
fats, but for our purposes, a better idea of their composi- 
tion may be gathered from a centesimal statement, viz. : 

CENTESIMAL COMPOSITION OF THE ELEMENTARY FATS. 

Stearin. Palmitin. Olein. 

Carbon 76.6 75.9 77.4 

Hydrogen 12.4 12.2 11.8 

Oxygen 10.0 11.9 10.8 

100.0 100.0 100.0 

Saponification. — The fats are characterized by forming 
soaps when heated with strong potash or soda-lye. They 
are by this means decomposed, and give rise to fatty 

* Margarin, formerly thought to be a chemically-distinct fat, is a mix- 
ture of stearin and palmitin. Oleomargarine is the commercial designa- 
tion of an artificially-obtained mixture of fats, animal or vegetable, 
that has nearly the consistence of dairy butter. 



80 HOW CROPS GROW. 

acids, which remain combined with the alkali-metal, 
and to glycerin, a substance which acts as a base. The 
fats are therefore termed glycerides. 

Exp. 41.— Heat a bit of tallow with strong solution of caustic potash 
until it completely disappears, and a soap, soluble in water, is obtained. 
To one-half the hot solution of soap, add hydrochloric acid until the lat- 
ter predominates. An oil will separate which gathers at the top of the 
liquid, and, on cooling, solidifies to a cake. This is not, however, the 
original *f at. It has a different melting point, and a different chem- 
ical composition. It is composed of the three fatty acids, corres- 
ponding to the elementary fats from which it was produced. 

When saponified by the action of potash, stearin yields 
stearic acid, Oi 8 H 36 2 ; palmitin yields palmitic acid, 
Ci 6 H 32 2 ; and olein gives oleic acid, Ci 8 H 34 2 .* The 
so-called stearin candles are a mixture of stearic and 
palmitic acids. The glycerin, C 3 H 8 3 , that is simul- 
taneously produced, remains dissolved in the liquid. 
Glycerin is found in commerce in a nearly pure state, as 
a colorless, syrupy liquid, having a pleasant, sweet taste. 

The chemical act of saponification consists in the re-arrangement of 
the elements of one molecule of fat and three molecules of water into 
three molecules of fatty acid, and one molecule of glycerin. 

Palmitin. Water. Palmitic acid. Glycerin. 

C 51 H 98 6 -f 3(H 2 0) = 3(C 1C H 32 2 ) + C 3 H 8 3 

Saponification is likewise effected by the influence of strong acids 
and by heating with water alone to a temperature of near 400° F. 

Ordinary soap is nothing more than a mixture of stearate, palmitate, 
and oleate of potasssium or of sodium, with or without glycerin. Com- 
mon soft soap consists of the potassium compounds of the above- 
named acids, mixed with glycerin and water. Hard soap is usually the 
corresponding sodium-compound, free from glycerin. When soft soap 
is boiled with common salt (chloride of sodium), hard soap and chlo- 
ride of potassium are formed by transposition of the ingredients. On 
cooling, hard-soap forms a solid cake upon the liquid, and the glycerin 
remains dissolved in the latter. 

Relations of Fats to CarWiydrates. — The oil or fat of 
plants is in many cases a product of the transformation 
of starch or other member of the cellulose group, for the 
oily seeds, when immature, contain starch, which van- 

* Oleic acid differs from stearic acid in containing two atoms less of 
hvdrogen, and is one of a series that bear this relation to the fatty acids 
of corresponding content of carbon. 



THE VOLATILE PART OF PLANTS. 87 

ishes as they ripen, and in the sugar-cane the quantity 
of wax is said to be largest when the sugar is least abund- 
ant, and vice versa. In germination the oil of the seed 
is converted back again into starch, sugar, etc. 

The Estimation of Fat (including wax) is made by warming the pul- 
verized and dry substance repeatedly with renewed quantities of ether, 
or sulphide of carbon, as long as the solvent takes up anything. On 
evaporating the solutions, the fat remains, and after drying thorough- 
ly, may be weighed. The ether extract thus obtained is usually accom- 
panied by a small amount of other substances, especially chlorophyll 
and lecithin, and is hence properly termed crude fat. 

PROPORTIONS OF CRUDE FAT IN VARIOUS VEGETABLE PRODUCTS. 

Per cent. Per cent. 

Meadow grass 0.8 Turnip 0.1 

Red clover (green) 0.7 "Wheat kernel 1.6 

Cabbage 0.4 Oat " 1.6 

Meadow hay 3.0 Maize " 7.0 

Cover hay 3.2 Pea " 3.0 

Wheat straw 1.5 Cotton seed 34.0 

Oat straw 2.0 Flax " 34.0 

Wheat bran 1.5 Colza " 45.0 

Potato tuber 0.3 

6. The Albuminoids or Troteids. — The bodies of 
this class essentially differ from those of the groups hith- 
erto noticed, in the fact of their containing, in addition 
to carbon, oxygen, and hydrogen, 15 to 18 per cent of 
nitrogen, with a small quantity of sutyhur, and, in some 
cases, perhaps phosphorus. 

These bodies, though found in some proportion in all 
parts of plants, being everywhere necessary to growth, 
are chiefly accumulated in the seeds, especially in those 
of the cereal and leguminous grains. 

The albuminoids or proteids* that occur in plants are 
so similar, in many characters, to those which constitute 
a large portion of every animal organism, that we may 
advantageously consider them in connection with the 
latter. 



* The nomenclature of these substances is unavoidably confused. 
They are often termed nitrogenous or nitrogenized bodies, also albu- 
minous bodies, and protein bodies. The term albuminoids has been 
latterly restricted, bv some authors, to the substances of which gela- 
tine is a type. The" word albuminates is applied to syntonin and 
casein. 



88 HOW CROPS GROW. 

Three familiar representatives of this class of bodies 
are, albumin, or the white of egg ; fibrin, or the clot of 
blood, and casein, which yields the curd of milk. 

General Characters. — Many of these substances occur 
in two very distinct modifications, one form being soluble 
in water, or in highly-diluted acids or alkalies, or in salt- 
solutions, the other insoluble in these liquids. 

Some of the soluble proteids we find naturally dissolved 
in the juices of living plants and animals. Some may be 
obtained in the solid form by evaporating off at a very 
gentle heat the water which is naturally associated with 
them. They then appear as nearly colorless or yellow- 
ish, amorphous solids, destitute of odor or taste, which 
dissolve again in water, but are insoluble in alcohol. 

Soluble compounds of proteids with magnesium or 
iron occur in plants, or may be obtained from the blood 
of animals, in the form of white or red crystals. 

Solutions of most of the albuminoids are readily coagu- 
lated by heat and by concentrated mineral acids, the 
albuminoids being thereby themselves chemically changed 
and made insoluble. Some coagulate spontaneously. 

The insoluble albuminoids, some of which also occur 
naturally in plants and animals, are, when purified as 
much as possible, white, flocky, lumpy or fibrous bodies, 
quite odorless and tasteless. 

The albuminoids, when subjected to heat, melt and 
burn with a smoky flame and a peculiar odor — that of 
burnt hair or horn — while a shining charcoal remains 
which is difficult to consume. 

Tests for the Albuminoids.— The chemist employs the behavior of 
the albuminoids towards a number of reagents * as tests for their pres- 
ence. Some of these are so delicate and characteristic as to allow the 



* Reagents are substances commonly employed for the recognition 
of bodies, or, generally, to produce chemical changes. All chemical 
phenomena result from the mutual action of at least two elements, 
which thus act and react on each other. Hence the substance that 
excites chemical changes is termed a reagent, and the phenomena or 
results of its application are called reactions. 



THE VOLATILE PART OF PLANTS. 89 

distinction of this class of substances from all others, even in micro- 
scopic observations. 

1. Solution of iodine colors them intensely yellow or bronze. 

2. Warm and strong hydrochloric acid colors these bodies blue, 
violet, or brown, or, if applied in large .excess, dissolves them to a 
liquid of these colors. 

3. In contact with nitric acid, especially when hot, they are stained a 
deep and vivid yellow. Silk and wool, which consist largely of pro- 
teids, are commonly dyed or printed yellow by means of nitric acid. 

4. A solution of mercuric nitrate in excess of nitric acid,* tinges them 
of a deep red color. This test enables us to detect albumin, for exam- 
ple, even where it is dissolved in 20,000 parts of water. 

5. With caustic soda and very dilute solution of copper sxdphate, 
successively applied, the proteids give a violet color which is intensi- 
fied by warming. (Biuret test.) 

The Albumins are soluble in water; the solutions as 
naturally occurring, unless very dilute, are coagulated by 
heat. 

Egg Albumin. — The white of a hen's egg on drying 
yields about 12 per cent of albumin in a state of tol- 
erable purity. The fresh white of eggs serves to illus- 
trate the peculiarities of this substance, and to exhibit 
the deportment of the albuminoids generally toward the 
above-named reagents. 

Exp. 42.— Beat or whip the white of an egg so as to destroy the deli- 
cate transparent membrane in the cells of which the albumin is held, 
and agitate a portion of it with water ; observe that it mostly dissolves 
in the latter. The solution is turbid from presence of globulin. 

Exp. 43. — Heat a part of the undiluted white of egg in a tube or cup. 
At 165° F. it becomes opaque, white, and solid (coagulates), and is con- 
verted into the insoluble modification. A higher heat is needful to 
coagulate solutions of albumin, in proportion as they are diluted with 
water. 

Exp. 44.— Add strong alcohol to a portion of the solution of albumin 
of Exp. 42. It precipitates the albumin, which for a time remains solu- 
ble in water, but later coagulates and becomes insoluble. 

Exp. 45.— Observe that albumin is coagulated by strong acids applied 
in small quantity, especially by nitric acid. 

Exp. 46.— Put a little albumin, either soluble or coagulated, into each 
of five test tubes. To one, add solution of iodine; to a second, strong 
hydrochloric acid ; to a third, nitric acid ; to a fourth, nitrate of mer- 
cury, and to the last a few drops of solution of copper sulphate, and 
then a little caustic soda or potash solution. Observe the characteristic 
colorations that appear immediately, or after a time, as described 
above. In the last four cases the reaction is hastened by a gentle heat. 



* This solution, known as Millon's reagent, is prepared by dissolving 
mercury in its own weight of nitric acid of sp. gr. 1.4, heating toward 
the close of the process, and finallv adding to the liquid twice its bulk 
of water. 



90 HOW CROPS GROW. 

Serum Albumin occurs dissolved in the blood, in milk, 
and in nearly all the liquids of the healthy animal body ex- 
cept the urine. Its characters are slightly different from 
those of egg-albumin. * The albumin of the blood may 
be separated by heating blood-serum (the clear yellow 
liquid that floats above the clot). The albumin of milk 
coagulates when milk-serum (whey) is heated to near 
boiling. 

On boiling entire milk, albumin coagulates, and, mixed 
with, fat and casein, is deposited as a tough coating on 
the sides of the vessel. 

Animal albumin remains, when its solutions are evap- 
orated at a temperature below 140° F., as a yellowish trans- 
lucent and friable solid, which easily dissolves in water. 

Vegetable Albumin. — In the juices of all plants is 
found in small quantity a substance which agrees in 
many respects with animal albumin, and has been termed 
vegetable albumin. The clear juice of the potato tuber 
(which may be procured by grating potatoes, squeezing 
the pulp in a cloth, and letting the liquor thus obtained 
stand in a cool place until the starch has deposited) con- 
tains such a body in solution, as may be shown by heat- 
ing to near the boiling point, when a coagulum separates, 
which, after boiling successively with alcohol and ether 
to remove fat and coloring matters, in its chemical reac- 
tions and composition closely approaches the coagulated 
albumin of eggs. 

The juice of succulent vegetables, as cabbage, yields 
a similar substance in larger quantity, though less pure, 
by the same treatment. 

Water which has been agitated for some time in con- 
tact with flour of wheat, rye, oats, or barley, is found 
by the same method to have extracted an albuminoid from 
these grains. 

The coagulum, thus prepared from any of these sources, exhibits the 
reactions characteristic of the albuminoids, when put in contact with 
nitrate of mercury, nitric or hydrochloric acid. 



THE VOLATILE PART OF PLANTS. 91 

Exp. 47.— Prepare impure vegetable albumin from potatoes, cabbage, 
or flour, as above described, and apply the nitrate of mercury test. 

As already intimated, albumin is chemically changed 
or decomposed in the process of coagulation. Coagu- 
lated albumin is not readily dissolved by dilute acids or 
by dilute aqueous solutions of alkali. 

The so-called vegetable albumin is mostly known only 
after coagulation by heat, and has been but imperfectly 
studied. According to Kitthausen, the coagulum ob- 
tained by heating the juice of potato tubers or the aque- 
ous extracts of peas and horse-beans ( Vicia faba) is solu- 
ble in dilute potash and in acetic acid; it is therefore 
not albumin. Sidney Martin reports a genuine albumin 
in the juice of the papaw, but its composition has not 
been determined. 

Fibrin. — Animal Fibrin is insoluble in water, alco- 
hol and salt-solutions ; it swells up in dilute acids, dis- 
solves in alkalies, and is coagulated by heat. 

The blood of the higher animals, when in the body or 
when fresh drawn, is perfectly fluid. Shortly after it is 
taken from the veins it partially solidifies — it coagulates 
or becomes clotted. It hereby separates into two por- 
tions, a clear, pale-} T ellow liquid — the serum — and the 
clot. As already stated, the serum contains albumin. 
On persistently squeezing and washing the clot with 
water, the coloring matter of the blood is removed, and 
a white stringy mass remains, which consists chiefly of 
fibrin, being a decomposition-product of another albu- 
minoid, fibrinogen. 

In very dilute hydrochloric acid, fibrin swells up, but 
does not dissolve. When freshly prepared, it absorbs 
oxygen from the air and gives off carbon dioxide. Heat- 
ing to 176° to 212° coagulates and shrinks it, and ren- 
ders it less elastic and incapable of absorbing oxygen. 

Exp. 48.— Observe the separation of blood into serum and clot ; coag- 
ulate the albumin of the former by heat, and test it with warm hydro- 
chloric acid. Tie up the clot in a piece of muslin, and squeeze and 



92 HOW CROPS GROW. 

wash in water until coloring matter ceases to run off. Warm it with 
nitric acid as a test. 

Flesh- Fibrin. — If a piece of lean beef or other dead 
animal muscle be repeatedly squeezed and washed in 
water, the coloring matters are gradually removed and a 
white residue is obtained which resembles blood-fibrin in 
its external characters, and as it represents the fibers of 
the original muscle, and was supposed to be a simple 
albuminoid, it was formerly designated flesh-fibrin. It 
is, however, a mixture consisting largely of myosin (see 
p. 97). It mostly dissolves in very dilute hydrochloric 
acid to a clear liquid, from which addition of much com- 
mon salt, or of a little alkali, throws down syutonin. 
The term flesh-fibrin is therefore no longer properly em- 
ployed to designate a distinct chemical substance. 

Vegetable fibrin. — When wheat-flour or rye-flour is 
mixed with a little water to a thick dough, and this is 
washed and kneaded for some time in water, the starch 
and albumin are mostly removed, and a yellowish tena- 
cious mass remains, which bears the name gluten. When 
wheat is slowly chewed, the saliva carries off the starch 
and other matters, and the gluten mixed with bran is 
left behind — well-known to country lads as " wheat- 
gum." 

Exp. 49.— Wet a handful of good, fresh, wheat-flour slowly with a lit- 
tle water to a sticky dough, and squeeze this under a fine stream of 
water until the latter runs off clear. Heat a portion of this gluten with 
Millon's reagent. 

Gluten is a mixture of several albuminoids, and con- 
tains also some starch and fat. When boiled with alco- 
hol it is partially dissolved.* The portion insoluble in 



* The dissolved portion Ritthausen found to consist of two distinct 
albuminoid or rather glutinoid bodies, viz. : 

Gliadin, or vegetable glue, is very soluble in water and alcohol. It 
strongly resembles animal glue and chiefly gives to wheat dough its 
tenacious qualities. 

Mucedin resembles gliadin, but is less soluble in strong alcohol, and 
is insoluble in water. When moist, it is yellowish-white in color, has 
a silkv luster, and slimy consistence. It exists also in gluten made 
from rye grain. (Ritthausen. Jour. fUr Prakt. Chcm., 83, 141, anddQ, 463.) 



THE VOLATILE PART OF PLANTS. 93 

strong alcohol Liebig first designated as vegetable fibrin. 
Kitthausen found this to be a mixture of two bodies, 
which he distinguished as gluten-casein and gluten -fibrin. 
The latter is extracted from gluten by hot weak alcohol 
and separates on partially removing the alcohol by evap- 
oration. 

The albuminoids of crude gluten dissolve in very dilute potash-solu- 
tion (J to 1 parts potash to 1,000 parts of water), and the liquid, after 
standing some days at rest, may be poured off from any residue of 
starch. On adding acetic acid in slight excess, the purified albuminoids 
are separated in the solid state. By extracting successively with weak, 
with strong, and with absolute alcohol, the gluten-casein of Kitthausen 
remains undissolved. 

On evaporating the alcoholic solution to one-half, there separates, on 
cooling, a brownish-yellow mass. This, when treated with absolute 
alcohol, leaves gluten-fibrin nearly pure. 

Vegetable fibrin is readily soluble in hot dilute alcohol, 
but slightly so in cold dilute, and not at all in absolute al- 
cohol. On prolonged heating with alcohol, it becomes in- 
soluble in that liquid. It does not dissolve in water. It 
has no fibrous structure like animal fibrin, but forms, 
when dry, a tough, horn-like mass. In composition it 
approaches washed muscle, but differs considerably from 
blood-fibrin. 

Wheat contains or yields* but a small proportion of 
fibrin and less appears to exist in hard than in the soft 
wheats. Eye contains less than wheat. Barley, from 
which no gluten can be got, yields to alcohol a small pro- 
portion of fibrin. 

Maize-fibrin, Zein. — The meal of Indian corn, unlike 
that of wheat and rye, when made into a dough, forms 
no gluten, but it yields to warm, weak alcohol some 
7 per cent of fibrin quite similar to that from wheat, 
though of somewhat different composition. 



* Weyl and Bischof believe that gluten does not pre-exist in wheat 
and rye, just as fibrin does not exist in living blood, but is a result of 
chemical change during the wetting and kneading of the flour to a 
dough. According to them a strong solution of common salt extracts 
from wheat flour vegetable globulin (see p. 97), and the residue, when 
kneaded with water, forms no gluten. If, however, the salt solution of 
globulin, in contact with the flour, is largely diluted with water, the 
flour will yield gluten by kneading. 



94 HOW CROPS GROW. 

Casein. — Animal Casein is the peculiar albuminoid of 
milk, in which it exists dissolved to the amount usually 
of 3 to 6 per cent. By saturating milk with magnesium 
sulphate the casein separates as an opaque white precipi- 
tate. Thus obtained it is freely soluble in water. Casein 
is also precipitated from milk by adding a little acetic or 
other acid, but is then nearly insoluble in water, has 
a decided acid reaction, and reddens blue litmus. The 
spontaneous curdling of milk, after standing at or- 
dinary temperatures for some time, appears to be directly 
due to the lactic acid which develops from milk-sugar as 
the milk sours. When milk is swallowed by a mamma- 
lian animal it curdles directly, and in the making of cheese 
the casein of milk is coagulated by the use of rennet, which 
is an infusion of the membrane lining the calf's stomach. 
Coagulated casein, though insoluble in water, dissolves 
in very dilute acids, and also in very dilute alkalies. 

The coherent cheese curd which is separated, from milk 
by rennet is doubtless a decomposition-product of casein, 
and carries with it a considerable portion of the phosphates 
and other salts of the milk. These salts are not found in 
the casein precipitated by acids, being kept in solution 
by the latter, but casein appears to contain a small amount 
of phosphorus (equivalent to 0.9 per cent phosphoric 
oxide) in organic combination. Skim-milk cheese, when 
new, consists mainly of coagulated casein with a little 
fat. Cheese made from entire milk contains most of the 
fat of the milk. 

Exp. 50.— Observe the coagulation of casein when milk is treated 
•with a few drops of dilute hydrochloric acid. Test the curd with 
nitrate of mercury. 

Exp. 51.— Boil milk with a little magnesium sulphate (Epsom salts) 
until it curdles. 

Vegetable Casein. — Several distinct substances have 
been described as vegetable caseins. Our knowledge with 
regard to tkem is in many important respects very defi- 
cient. Even their elementary composition is a matter of 
uncertainty. 



THE VOLATILE PART OF PLANTS. 95 

Gluten- Casein. — That part of the gluten of wheat 
which is insoluble in cold alcohol is digested in a highly 
dilute solution of potash, and the clear liquid is made 
faintly acid by acetic acid. The curdy white precipitate 
thus obtained, after washing with water, alcohol and 
ether, and dried, is the gluten-casein of Eitthausen. It 
is insoluble in water, and in solutions of common salt, 
easily soluble in weak alkalies and coagulated by acids. 
Eitthausen obtained this body from wheat, rye, barley, 
and buckwheat. 

Legumin is the name that has been applied to the chief 
albuminoid of oats, peas, beans, lupins, vetches, and other 
legumes. It is extracted from the pulverized seeds by 
dilute alkalies, and is thrown down from these solutions 
by acids. From some leguminous seeds it may be partially 
extracted by pure water, probably because of the presence 
of alkali-phosphates which serve to dissolve it. It is 
generally mixed with conglutin, from which it may be 
separated by soaking in weak brine (a 5 per cent solution 
of common salt). Thus obtained, it is insoluble in pure 
water and in brine, but soluble in dilute alkalies, and has 
a decided acid reaction. Legumin, as existing in the 
horse-bean ( Viciafaba), is soluble in brine, but after solu- 
tion in alkali and precipitation with acids, is insoluble 
in salt solution. The casein, animal or vegetable, that 
is thrown down from salt-solution by acids is evidently a 
chemical compound of the original proteid with the acid 
(acid-proteid). 

Exp. 52.— Prepare a solution of vegetable casein from crushed peas, 
almonds, or pea-nuts, by soaking them for some hours in warm water, 
to which a few drops of dilute ammonia-water or potash-lye has been 
added, and allowing the liquid to settle clear. Precipitate the casein 
by addition of an acid to the solution. 

The Chinese are said to prepare a vegetable cheese by 
boiling peas to a pap, straining the liquor, adding gypsum 
until coagulation occurs, and treating the curd thus ob- 
tained in the same manner as practiced with milk-cheese, 



% HOW CROPS GROW. 

viz. : salting, pressing, and keeping until the odor and 
taste of cheese are developed. It is cheaply sold in the 
streets of Canton under the name of Tao-foo. Vegetable 
casein appears to occur in small quantity in the potato, 
and many plants ; and may be exhibited by adding a few 
drops of acetic acid to turnip juice, for instance, which 
has been freed from albumin by boiling and filtering. 

The Globulins are insoluble in water, but dissolve in 
neutral salt-solutions. Some dissolve only in salt-solu- 
tions of moderate strength and are thrown down from 
these solutions by more salt. Others are soluble in sat- 
urated salt-solutions. They are coagulated by heat. 
Some animal globulins may first be noticed. 

Vitellin is obtained from the yolk of eggs ; fat and 
pigment are first removed by ether, and the white residue 
is dissolved in a solution of common salt (1 of salt to 10 
of water). Addition of water to the filtered* solution 
separates the vitellin as a white, flocky mass. 

Paraglobulin exists in blood serum, and may be 
thrown down by saturating the serum with magnesium 
sulphate. It may be obtained in transparent microscopic 
disks that are probably crystalline. Its solutions in brine 
coagulate by heat, like albumin. 

Fibrinogen. — When blood fresh from the veins of the 
horse is mixed directly with a saturated aqueous solution 
of magnesium sulphate, fibrinogen dissolves, and the 
liquid, after filtering from the red corpuscles, upon mix- 
ing with a saturated brine of common salt, deposits this 
body in white flocks, which unite to a tough, elastic 
mass. Its solutions in brine coagulate at a lower tem- 
perature than those of paraglobulin. 

Fresh-drawn blood, after standing a short time, coag- 
ulates of itself to a more or less firm clot. Under the 
microscope this process is seen to consist in the rapid 
formation of an intricate net-work of delicate threads or 
fibrils. These are fibrin, and come from the coagulation 



THE VOLATILE PART OF PLANTS. 97 

of fibrinogen. Coagulation here appears to be induced 
by a ferment whose effect is suspended by strong saline 
solutions, but is renewed when these are mixed with 
much water. This ferment occasions decomposition of 
the fibrinogen, fibrin being one of the products. The 
fibrin-ferment is supplied from ruptured white blood- 
corpuscles. The chemical composition of fibrinogen and 
fibrin, as determined by analysis, is quite the same. 

Myosin. — Lean beef or other dead muscle-tissue, after 
mincing and washing with water to remove coloring mat- 
ters, is soaked in 10 per cent salt-solution. Myosin dis- 
solves and is precipitated from the filtered brine by diluting 
with water. It dissolves also in dilute hydrochloric acid 
and in dilute potash solution. Strong hydrochloric acid 
converts it into syntonin. Myosin does not exist in liv- 
ing muscle, but is formed after death, during rigor mor- 
tis, from the juices of the muscles by a process of coag- 
ulation. Its formation is accompanied by the develop- 
ment of lactic and carbonic acids. Myosin is the chief 
ingredient of what was formerly known as muscle-fibrin. 

Vegetable Globulins occur abundantly in seeds where 
they are chief ingredients of the so-called aleurone or 
protein-granules. From these protein-granules, or from 
the pulverized seeds, the globulins are extracted by salt- 
solutions and by weak alkalies. The globulin which 
water alone extracts from many seeds is dissolved by help 
of the salts, which are there present. Such saline ex- 
tracts are coagulated by heat and thus globulins have 
figured, no doubt, as " vegetable albumin-" Some glob- 
ulins are only known in the amorphous or granular state ; 
others occur as crystals. 

Conglutin exists abundantly, according to Eitthausen, 
in the seeds of peach, almond, lupin, radish, pea-nut, 
hickory-nut, and hazel-nut, where it is usually associated 
with legumin. It may be separated by weak brine, in 
which it is invariably soluble, while legumin, after sepa- 
7 



98 HOW CHOPS GROW. 

ration from alkali-solutions, is undissolved by brine. The 
conglutin obtained from lupins and pea-nuts differs some- 
what from that found in the hazel-nut, and in almond 
and peach seeds. Conglutin cannot be crystallized from 
salt-solutions, as readily happens with vegetable vitellin. 

Vegetable Vitellin. — Applying this designation to al- 
buminoids which are insoluble in water, but dissolve in 
saturated salt-solutions, and are thence precipitated by 
water, we find vitellin more or less abundantly in seeds 
of squash, hemp, sunflower, lupin, bean, pea, Brazil-nut, 
castor-bean, and various other plants. It may be extracted 
from squash seeds by common-salt-solution (of 10 per 
cent) or dilute alkali. Diluting the brine with water or 
neutralizing the alkali with acids precipitates the vitellin, 
which, after washing with water, alcohol and ether, may 
be obtained in crystals (microscopic octahedrons) by dis- 
solving in warm brine and slowly cooling. From seeds 
of hemp and castor-bean Ritthausen obtained crystals 
identical in appearance and composition with those of 
squash seeds, but soluble in water, probably because of 
the presence of alkali salts. 

Vegetable Myosin. — Weyl and Bischof consider that 
cereal and leguminous seeds contain or yield myosin anal- 
ogous to muscle-myosin, which differs from vitellin (and 
conglutin) in being precipitated from its solution in weak 
brine by saturating the same with salt. They find that 
wheat-flour contains but little if any proteid besides 
myosin, and that when this is removed from the flour by 
salt-solution or by very weak soda-lye or ^y hydrochloric 
acid of 0.1%, the residue is incapable of yielding gluten. 
Gluten is therefore a decomposition-product of myosin. 
These results are confirmed by the recent work of Mar- 
tin (Jour, of Physiology, 1887). Zoeller found that the 
pulp of potatoes, after starch and soluble matters had 
been removed by copious washings with water, yielded to 
10% salt-solution an albuminoid which separated when the 



THE VOLATILE PART OF PLANTS. 99 

brine was saturated by addition of salt in excess. He also 
precipitated myosin from the juice of the tubers by sat- 
urating it with salt. 

The myosins are precipitated by conversion into alkali- 
proteids, when their brine-solutions are deprived of salt 
by dialysis or when these solutions are kept for some 
hours at 100° F. (Sidney Martin.) 

Vegetable Paraglohalin is recently stated to exist in 
papaw-juice, and in the seeds of lequirity, Abrus preca- 
torius. It is distinguished from myosin by requiring a 
higher temperature for coagulation from salt-solutions 
and in not suffering conversion into an insoluble alkali- 
proteid by dialysis or long heating to 100° F. (Mai-tin.) 
Acid-Proteids are bodies formed from proteids by the 
prolonged action of acids. They are insoluble in water, 
alcohol and brines, but easily soluble in dilute acids or 
alkalies, and are precipitated by neutralizing these solu- 
tions. The solutions of acid-pro teids in acids are not co- 
agulable by heat. The albumins and globulins are grad- 
ually converted into acid-proteids by cold, highly dilute 
acids, and more rapidly by stronger acids and gentle heat. 
Syntonin is the acid-proteid resulting from solution of 
muscle-flesh, or myosin, in weak hydrochloric acid, and is 
thrown down when the solution is neutralized by an 
alkali, as a white gelatinous substance. Acid-proteids 
may exist in seeds such as the oat, lupin, pea, bean, etc., 
which contain so much free acid, or acid salt, that the 
water extract is strongly acid to test-papers. 
• Alkali-Proteids, or Albuminates. — The action of 
dilute alkali -solutions on most proteids converts them 
into bodies which, like acid-proteids, are insoluble in 
water and salt-solutions, but soluble in dilute acids and 
alkalies, and are thrown down from these solutions by 
neutralization. Dilute acids do not convert them into 
acid-proteids. Alkali-jrroteids are said to exist gener- 
ally in the young cells of the animal, and may also occur 



100 HOW CROPS GROW. 

in plants in the alkaline juices of the cambium. The 
"vegetable caseins/' viz., legumin and gluten-casein, as 
they occur in the alkaline juices or extracts of plants, 
are probably bodies of this class, and when precipitated by 
acids unite to the latter, forming compounds with an 
acid reaction. Casein of milk has been by some consid- 
ered to be an alkali-proteid, but is probably distinct. 

Proteoses and Peptones. — These terms designate 
bodies that result from the chemical alteration of albu- 
minoids, under the influence of "ferments" which exist 
in plants, but which have been most fully studied as they 
occur in the digestive apparatus of animals. 

The albuminoids, as found in plants, are mostly insol- 
uble in the vegetable juices, and those which are soluble 
(probably because of the presence of salts, acids or alka- 
lies) are mostly incapable of freely penetrating the cell- 
membranes which inclose them, and cannot circulate in the 
vegetable juices, and likewise, when they become the food 
of animals, cannot leave the alimentary canal so as to be- 
come incorporated with the blood until they have been 
chemically changed. During the processes of animal 
digestion the albuminoids of whatever kind undergo solu- 
tion and conversion into bodies which are freely soluble 
in water, aud rapidly penetrate the moist membranes of 
the intestines, and thus enter into the circulation. These 
bodies have been prepared for purposes of study by a 
partly artificial digestion, carried on in glass vessels with 
help of the digestive ferments obtained from the stomach 
(pepsin) or pancreas (trypsin) of animals.* 

It appears from Kiihne and Chittenden's investigations 
that a series of soluble and diffusible products are formed 
from each albuminoid with progressive diminution of 
carbon and increase of oxygen, and, in some cases, of 
nitrogen. The first-formed products are termed pro- 



* Reference may be had to Chittenden's Studies in Physiological 
Chemistry, Connecticut Acad., Vols. II and III, 1887 and 1889. 



THE VOLATILE PART OF PLANTS. 101 

teoses (albnmoses, caseoses, globidoses, etc.) ; those last 
produced they designate peptones, but investigators are 
not as yet agreed as to the precise application of these 
terms. What have been formerly called peptones are 
now considered to be largely proteoses. 

The composition of some of these bodies may be seen 
from the following analyses by Chittenden and Painter : 

c. h. n. s. o. 

Casein 53.30 7.07 15.91 0.82 22.03 

Protocaseose 52.50 7.15 15.73 0.96 23.86 

Deuterocaseose 51.59 6.98 15.73 0.75 25.03 

Casein-Peptone 49.94 6.51 16.30 0.68 26.57 

Of the several products which have been analyzed and 
classed as proteoses and peptones, it is not certain that 
any one is a strictly homogeneous substance. It is more 
than probable that some of them are mixtures. The 
proper use of these names is provisional, to characterize 
certain evidently distinct stages of albuminoid metamor- 
phosis, whose exact nature can only be cleared up by 
further investigation. 

The peptones may be defined as the final products of 
the action of the peptic ferment. They are soluble in 
water and freely diffusible through animal membranes. 
The albumoses (or proteoses) are intermediate between 
the albuminoids and the peptones, being mostly soluble 
in water but not freely diffusible. 

The proteoses much resemble the albuminoids from 
which they are derived, not only in composition, but in 
many of their properties. The peptones have less re- 
semblance, but appear capable of partially reverting to 
proteoses, as some of the latter are said to yield coagula- 
ble albuminoids when kept in the moist state. 

Weak acids and alkalies also convert the albuminoids 
into proteoses and peptones, and probably the acid-pro- 
teids, perhaps also the alkali-proteids, already mentioned, 
contain proteoses in admixture. Since pepsin-digestion 
requires the aid of a free acid and trypsin-digestion sue- 



102 HOW CROPS GROW. 

ceeds best in presence of a free alkali, the conditions 
under which the proteoses of digestion are formed are in 
part identical with those that give rise to the acid-pro- 
teids and alkali-proteids. 

Peptones have been found in small proportions in the 
water-extract of various plants, e. g., seedlings, lupins, 
barley-malt, young grass, alfalfa, etc. (Vs. St., XXIV, 
363, 371, 440, and XXXII, 389.) 

Vines has found a proteose in considerable quantity in 
the seeds of lupin, peony, and wheat and in the Brazil- 
nut and castor-bean, and considers bodies of this class to 
be of general occurrence in the protein-granules of plants. 

The proteose (hemialbumose*) from lupins has, exclu- 
sive of 0.81 p. c. of ash, the following composition per 
cent according to Vines : 



c. 


H. 


N. 


S. 


O. 


52.58 


7.24 


14.87 


1.52 


23.79 



Sidney Martin reports the existence of a proteose 
(hemialbumose) in the juice of the papaw or melon 
tree (Carica papaya) where it is associated with the fer- 
ment papain, which is very similar to that of the pan- 
creatic secretion of animals. 

Ferments are substances which produce or excite 
chemical changes in a manner as yet mostly unexplained, 
the ferments themselves not appreciably contributing of 
their own substance to the products of the processes 
which they set in operation. 

The ferments that figure in agricultural chemistry are 
closely related to and apparently derived from the albu- 
minoids, but in no case has their chemical composition 
been positively established. They are distinguished and 
characterized almost solely by the sources whence they 
are derived, and the effects which they produce. The 



*Kiihne first distinguished the products of pepsin or trypsin diges- 
tion into hemialbumose and antialbumose, the former being converted 
by trypsin into amido-acids (see p. 114), the latter remaining unaltered 
by the digestive ferments. Kuhne & Chittendon have more recently 
shown " hemialbumose " to be a mixture mainly of proto and dentero- 
albumose. 



THE VOLATILE PART OE PLANTS. 103 

substances which the chemist can prepare, and to which 
he gives special designations, are doubtless mixtures, and 
in most cases contain but a small proportion of the real 
ferment, which, in a state of entire purity, is unknown. 

Leaven, or Yeast, which has been employed in mak- 
ing bread, wine and beer for many centuries, contains, or 
mainly consists of, a microscopic plant of very simple 
structure (pp. 244-5), which, when placed in a solution of 
cane-sugar, is able in the first place to cause the " inver- 
sion " of that substance into the two sugars, dextrose and 
levulose, and, secondly, to transform both the latter into 
alcohol and carbon dioxide. The " inverting " effect of 
yeast upon cane-sugar has been traced to a substance 
which can be separated from the yeast and obtained as a 
dry, white powder. The alcoholic fermentation requires 
the living yeast plant for its accomplishment. Ferments 
are accordingly divided into the two classes, unorganized 
and organized. We shall here notice briefly a few unor- 
ganized ferments or enzymes,, as they are also termed, 
that have been somewhat carefully studied. 

Invertin is obtained from dry, pulverized yeast by 
heating it to 212° to coagulate albumin and then ex- 
tracting with warm water. The invertin dissolves, and, 
by addition of alcohol, is precipitated. Barth thus ob- 
tained a substance containing 6 per cent of nitrogen 
which was able, in the course of 48 hours, to transform 
(invert) 760 times its weight of cane-sugar. Invertin 
has no effect on starch or dextrin. 

Diastase is the name applied to a substance that may be 
obtained as a whitish powder from sprouted barley (malt) 
by extracting with dilute alcohol and precipitation with 
strong alcohol, which is* capable of transforming 2,000 
times its weight of starch, first into dextrin and finally 
into maltose and dextrose. The purest diastase prepared 
by Lintner contained 10.4 per cent, nitrogen and gave 
reactions for albuminoids, but it had properties besides 



104 HOW CROPS GROW. 

its action on starch that strikingly distinguished it from 
the ordinary proteids. 

Pepsin is that ferment of the so-called gastric juice of 
the animal stomach which enables this organ to dissolve 
and "peptonize" the albuminoids of the food. It may 
be extracted from the inner coating of the stomach by 
glycerine or very dilute hydrochloric acid, and is precip- 
i table from these solutions by strong alcohol. Pepsin 
requires the presence of a free acid to dissolve the albu- 
minoids ; in neutral or alkaline solution it has no " di- 
gestive power." 

Trypsin is a ferment formed in the pancreas and exist- 
ing in the pancreatic juice which, in mammalian animals, 
during the digestion of food, is poured into the upper 
intestine, where it continues and completes the solution 
of albuminoids begun by the gastric juice. Trypsin acts 
in neutral but most effectively in alkaline solutions ; its 
operation is arrested by free acids. The results of its 
action differ in some respects from those of pepsin. 

Papain. — The milky juice of the Brazilian plant Car- 
ica papaya, or melon-tree, contains this ferment, which, 
like trypsin, is freely soluble in water, rapidly dissolves 
albuminoids, best in neutral or alkaline solutions, convert- 
ing them into proteoses and peptones. Papain itself, as 
obtained by Wurtz & Bouchut, has the properties and 
composition that characterize the proteoses. 

Ferments appear to perform very important functions 
in the vegetable as well as in the animal organism, and 
have to be referred to frequently as occasioning the con- 
version of insoluble into soluble substances, and of com- 
plex into simpler bodies. 

Composition of the Albuminoids. — There are va- 
rious reasons why the exact composition of some of the 
bodies just described is still a subject of uncertainty. They 
are, in the first place, naturally mixed or associated with 
other matters from which it is very difficult to separate 



THE VOLATILE PART OF PLANTS. 105 

them fully. Again, if we succeed in removing foreign 
substances, it must usually be done by the aid of acids, 
alkalies, salt-solutions, alcohol and ether, and there is 
reason to believe that in many cases these reagents essen- 
tially modify the properties and composition of the pro- 
teids. These bodies, in fact, as a class, are extremely 
susceptible to change and alter in respect to appearance, 
solubility, and other qualities that serve to distinguish 
them, without any corresponding change in chemical 
composition being discoverable by our methods of anal- 
ysis. On the other hand, the substances that have been 
prepared by different experimenters from the same 
sources, and by substantially the same methods, often 
show decided differences of composition. 

Finally, the methods of analysis used in determin- 
ing their composition are liable to considerable error, 
and, if applied to the pure substances, are scarcely 
delicate enough to indicate their differences with entire 
accuracy. 

In the accompanying table (p. 106) are given the most 
recent and trustworthy analyses of the various vegetable 
albuminoids, and of the corresponding substances of ani- 
mal origin. 

Referring to the analyses of Albumins we observe that 
the egg-albumin differs from serum-albumin in contain- 
ing about one per cent more of oxygen and one less of 
carbon, while hydrogen, nitrogen and sulphur are prac- 
tically the same. These two albumins have been very 
thoroughly studied, their difference of composition is 
well established, and they have positive differences in 
their properties, so that there can be little doubt thab 
they are specifically distinct substances. Of the Vegeta- 
ble Albumins none offer any reasonable guarantee of 
purity. The composition of barley-albumin is near that 
of the animal albumins, but it contains one-third less 
sulphur. So far, then, as present data indicate, the veg- 



106 



HOW CHOPS GROW. 



COMPOSITION OF ALBUMINOIDS. 



ALBUMINS. 



Egg 

Blood serum. 

Wheat 

Barley 



FIBRINS. 



Blood 

Gluten-fibrin, wheat. 
" " niaize . 

CASEINS. 



Milk casein * 

Gluten-casein, wheat. 



52.2 
53.1 
53.1 
52.8 



52.7 
54.3 
54.6 



53.3 
52.9 

52.8 



Gluten-casein, buckwheat*. 50.2 
Legumin, lupins 51.4 



GLOBULINS. 



Paraglobulin 

Fibrinogen, blood ... 

Myosin, beef 

Conglutin, lupin 

" hazel-nut 

Vitellin, squash 

" hemp (crystals). 

" Brazil-nut 



Gliadin, wheat. 



52.7 
52.9 
52.8 
50.1 
51.2 
51.3 
51.0 
52.4 

52.7 









« 


jl 




© 


*! 

^ 




^ 


&2 




15.8 


1.9 


23.2 


16.0 1.8 


22.2 



o 

^ -3 's 



G.9 

6.9 

7.2 17.6 1.6 20.5 

7.2 15.811.2 23.0 



6.816.9 1.1 22.5 
7.2 16.9 1.0|20.6 
7.515.5 0.7 21.7 



7115.9 0.8 22.0 
7.0 17.1 1.022.0 
15.8 1.1 23.3 
6.817.4 1.5 24.1 
7.0 17.5 0.6 23.5 



Analysts. 

Chittenden & Bolton. 
Hammarsten. 

Ritthausen. 



Hammarsten. 
Ritthausen. 



Chittenden & Painter. 
Ritthausen. 
Chittenden & Smith. 

| Ritthausen. 



Hammarsten. 



7.015.8 1123.4 | 

6.9 16.7 1.3 22.2 I 

7 . 1 16 . 8 1 . 3 ; 21 . 9 Chittenden & Cummins. 

7.0 18.7 11 23. OH 



7.118.6 
7.518.1 

7.018.7 



7.1 
7.1 



181 
18.0 



0.6 
0.6 
0.8 
0.5 

0.9 



22' gi ^Ritthausen. 

22^5 J 

Weyl. 



21.9 
21.3 



Ritthausen. 



Mucedin, wheat 541 6.916.6 0.9 21.5 Ritthausen. 

See pp. 101 and 102 for analyses of Proteoses and Peptone. 

etable albumins are not identical with those derived from 
the animal. 

As respects the Fibrins we have already seen that there 
is no similarity in properties between that of blood and 
those obtained from gluten. The analyses of the two 
gluten-fibrins show either that these substances are quite 
distinct or that they have not yet been obtained in the 
pure state. 

The Vegetable Caseins, as analyzed by Bitthausen, are 



*The analysis of milk casein should include 0.9 phosphorus. The 
buckwheat casein contained 0.9 phosphorus, which is not included in 
the analysis. Whether phosphorus is an ingredient of casein, or an 
" impurity," is not perhaps positively established. 



THE VOLATILE PART OF PLANTS. 107 

observed to contain more nitrogen by 1.2 to 1.6 per cent 
than exists in animal casein. Furthermore, they differ 
from each other so widely in carbon content (2. 7 per cent) 
as to make it highly probable that their true composition, 
was not in all cases correctly determined. 

This conclusion is justified by the results of Chittenden 
& Smith, who have recently analyzed five different prep- 
arations of gluten-casein, made from wheat by Eitthau- 
sen's method. The average of their accordant analyses 
is given above.* Since nitrogen was determined by two 
methods (those of Dumas and Kjeldahl) these analyses 
would appear to establish the composition Of gluten- 
casein, which accordingly closely agrees with that found 
by Eitthausen for "albumin" from barley, and with 
that of paraglobulin, and has the same nitrogen content 
as the casein of milk. 

The Animal Globulins agree in composition with each 
other as well as with animal fibrin which is formed from 
globulin (fibrinogen). The Vegetable Globulins are strik- 
ingly different in composition, containing 1.5 to 2 per 
cent more nitrogen and mostly but half as much sul- 
phur. The hazel-nut conglutin and the hemp-seed vitel- 
lin have the same composition. 

It is evident that the vegetable albuminoids, on the 
whole, are distinct from those of the animal, but their 
true composition and relations to each other, to a great 
extent, remain to be established. 

Some Mutual Relations of the Albuminoids. — It was 
formerly supposed that these bodies are identical in com- 
position, the differences among the analytical results 
being due to foreign matters, and that they differ from 
each other in the same way that cellulose and starch 
differ, viz. : on account of different arrangement of the 
atoms. Afterwards, Mulder advanced the notion that 
the albuminoids are compounds of various proportions 

* Kindly communicated by the authors. 



108 HOW CBOPS GROW. 

of hypothetical sulphur and phosphorus radicles with 
a common ingredient, which he termed protein (from 
the Greek signifying " to take the first place/' because 
of the great physiological importance of such a body). 
Hence the designations protein-bodies and proteids. 
The transformations which these substances are capable 
of undergoing sufficiently show that they are closely 
related, without, however, satisfactorily indicating in 
what manner. 

In the animal organism, the albuminoids of the food, 
of whatever name, are dissolved in the juices of the 
digestive organs, and pass into the blood, where they 
form blood albumin and globulin. . As the blood nour- 
ishes the muscles, they are modified into the flesh-albu- 
minoids ; on entering the mammary system they are 
converted into casein, while in the appropriate part of 
the circulation they are formed into the albumin of the 
egg, or embryo. 

In the living plant, similar changes of place and of 
character occur among these substances. 

The Albuminoids in Animal Nutrition. — We step 
aside for a moment from our proper plan to direct atten- 
tion to the beautiful adaptation of this group of organic 
substances to the nutrition of animals. Those bodies 
which we have just noticed as the animal albuminoids, 
together with others of similar composition, constitute 
a large share of the healthy animal organism, and espec- 
ially characterize its actual working machinery, being 
essential ingredients of the muscles and cartilages, as 
well as of the nerves and brain. They likewise exist 
largely in the nutritive fluids of the animal — in blood 
and milk. So far as we know, the animal body has not 
the power to produce a particle of albumin, or fibrin, or 
casein except by the transformation of similar bodies pre- 
sented to it from external sources. They are hence indis- 
pensable ingredients of the food of animals, and were 



THE VOLATILE PART OF PLAKTS. 109 

therefore designated by Liebig as the plastic elements of 
nutrition. They have also been termed the blood-build- 
ing or muscle-forming elements. It is, in all cases, the 
plant which originally constructs these substances, and 
places them at the disposal of the animal. 

The albuminoids are mostly capable of existing in the 
liquid or soluble state, and thus admit of distribution 
throughout the entire animal body, as in blood, etc. They 
likewise readily assume the solid condition, thus becom- 
ing more permanent parts of the living organism, as well 
as capable of indefinite preservation for food in the seeds 
and other edible parts of plants. 

Complexity of Constitution. — The albuminoids are 
highly complex in their chemical constitution. This fact 
is shown as well by the multiplicity of substances which 
may be produced from them by destructive and decom- 
posing processes as by the ease with which they are 
broken up into other and simpler compounds. Kept in 
the dissolved or moist state, exposed to warm air, they 
speedily decompose or putrefy, yielding a large variety of 
products. Heated with acids, alkalies, and oxidizing 
agents, they mostly give origin to the same or to anal- 
ogous products, among which no less than twenty differ- 
ent compounds have been distinguished. 

The numbers of atoms that are associated in the mole- 
cules of the proteids are very great, though not in most 
cases even approximately known. The Haemoglobin of 
blood, which forms red crystals that admit of preparing 
in a state of great purity, contains in 100 parts — 



c 


H 


N 


O 


S 


Fe 


54.2 


7.2 


16.1 


21.6 


0.5 


0.4 



The iron (Fe) is a constant and essential ingredient, and 
if one atom only of this metal exist in the haemoglobin 
molecule, its empirical formula must be something like 
C64oHioooN~i64FeS 2 190 , and its molecular weight over 14,- 
000. Haemoglobin readily breaks up into a proteid and a 



110 



HOW CHOPS GROW. 



much simpler red crystalline substance, Haemaeetin, yield- 
ing about 96 per cent of the former and 4 per cent of 
the latter. Haematin has approximately the formula 
C 3 2H 84 N 4 Fe0 6 , so that the proteid, though simpler than 
haemoglobin, must have an extremely complicated mole- 
cule, and it is, accordingly, difficult to decide whether a 
few thousandths of the acids, bases or salts which may 
be associated with these bodies, as they exist in plants or 
pass through the hands of the chemist, are accidental or 
essential to their constitution. 

Occurrence in Plants. — Aleurone. — It is only in the 
old and virtually dead parts of a living plant that albu- 
minoids are ever wanting. In the young and growing 
organs they are abundant, and exist dissolved in the sap 
or juices. They are especially abundant in seeds, and 
here they are often deposited in an organized form, chiefly 





oocod 




in grains similar to those of starch, and mostly insoluble 
in water. 

These grains of albuminoid matter are not, in many 
cases at least, pure albuminoids. Hartig, w r ho first de- 
scribed them minutely, has distinguished them by the 
name aleurone, a term which we may conveniently em- 
ploy. By the word aleurone is not meant simply an 



THE VOLATILE PART OF PLANTS. 



Ill 



albuminoid, or mixture of albuminoids, but the organ- 
ized granules found in the plant, of which the albumin- 
oids are chief or characteristic ingredients. 

In Fig. 18 is represented a magnified slice through the 
outer cells (bran) of a husked oat kernel. The cavities 
of these outer cells, a, c, are chiefly occupied with very 
fine grains of aleurone. In one cell, b, are seen the 
much larger starch grains. In the interior of the oat 
kernel, and other cereal seeds, the cells are chiefly occu- 
pied with starch, but throughout grains of aleurone are 
more or less intermingled. 

Fig. 19 exhibits a section of the exterior part of a 
flax-seed. The outer cells, a, contain vegetable muci- 
lage ; the interior cells, e, are mostly filled with minute 
grains of aleurone, among which droplets of oil, /, are 
distributed. 

In Fig. 20 are 
shown some of the 
forms assumed by in- ^ 
dividual albuminoid- a 
grains ; a is aleurone 
from the seed of the vetch, b from the castor-bean, c 
from flax-seed, d from the fruit of the bayberry (Myrica 
cerifera) and e from mace (an appendage to the nutmeg, 
or fruit of the Myristica moschata). 

Crystalloid aleurone. — It has been already remarked 




c 
Fig. 20. 





Fig. 21. 

that crystallized albuminoids exist in plants. This was 
first observed by Hartig {Entwickelungsgescliichte des 



112 HOW CROPS GROW. 

Pflanzenkeims, p. 104). In form they sometimes imitate 
crystals quite perfectly, Fig. 21, a; in other cases, b, 
they are rounded masses, having some crystalline planes 
or facets. They are soft, yield easily to pressure, swell 
up to double their bulk when soaked in weak acids or 
alkalies, and their angles have not the constancy peculiar 
to ordinary crystals. Therefore the term crystalloids, i.e., 
having the likeness of crystals, has been applied to them. 

As Cohn first noticed (Jour, fur Praht. Chem., 80, p. 
129), crystalloid aleurone may be observed in the outer 
portions of the potato tuber, in which it invariably pre- 
sents a cubical form. It is best found by examining the 
cells that adhere to the rind of a potato that has been 
boiled. In Fig. 21, a represents a cell from a boiled 
potato, in the center of which is seen the cube of aleurone. 
It is surrounded by the exfoliated remnants of starch- 
grains. In the same figure, b exhibits the contents of a 
cell from the seed of the bur reed (Sparganium ramo- 
sum), a plant that is common along the borders of ponds. 
In the center is a comparatively large mass of aleurone, 
having crystalloid facets. 

As already stated, the proteids in the crystalloid aleu- 
rones of hemp, castor-bean and squash have the chemical 
characters of globulin. The aleurone of the Brazil-nut 
(Bertholletia) and that of the yellow lupin contain, ac- 
cording to Hartig and Kubel, 9.4% of nitrogen which 
corresponds to some 50 or 60% of proteids. 

Weyl obtained from the Brazil-nut a very pure amor- 
phous vitellin with 18.1% of nitrogen. The vitellin of 
Brazil-nut, castor-bean, and of hemp and squash seeds has 
been recrystalized from salt solutions by Schmiedeberg, 
Drechsel, Griibler and Ritthausen. According to Vines, 
seeds of lupin and peony yield a myosin to salt-solution, 
and sunflower seeds, after treatment with ether to remove 
oil, yield a globulin with the properties of myosin, but if 
alcohol is used, the proteid has the character of vitellin. 



THE VOLATILE PART OF PLANTS. 113 

Vines, who has examined the aleurone of many plants, 
finds it in all cases more or less soluble in water. The 
globulin doubtless goes into solution by help of the salts 
present. Vines also states that a body soluble in water, 
having the properties of a proteose (hemialbumose) , is 
universally present in aleurone. 

Estimation of the Albuminoids. — The quantitative sep- 
aration of these bodies, as they occur in plants, is mostly 
impossible in the present state of science. In many cases 
their collective quantity in an organic substance may be 
calculated with approximate accuracy from its content of 
nitrogen. 

In calculating the nutritive value of a cattle-food the 
albuminoids are currently reckoned as equal to its nitro- 
gen multiplied by 6.25. This factor is the quotient ob- 
tained by dividing 100 by 16, which, some 25 years ago, 
when cattle-feeding science began to assume its present 
form, there was good reason to assume was the average 
per cent of nitrogen in the albuminoids. As Ritthausen 
has insisted, this factor is too small, since the albuminoids 
of the cereals and of most leguminous seeds, as well as of 
the various oil-cakes, contain nearer 17 than 16 per cent 
of nitrogen, if our analyses rightly represent their com- 
position, and the factor 6 (= 100 -f- 16.66) would be 
more nearly correct. 

This mode of calculation only applies with strictness 
where all the nitrogen exists in albuminoid form. This 
appears to be substantially true in most seeds, but in case 
of young grass and roots there is usually a considerable 
proportion of non-albuminoid nitrogen, for which due 
allowance must be made. (See Amides.) * 

* Ammonia, NH 3 , and Nitric acid, NH0 3 . These bodies are mineral, not 
organic substances, and are not, on the whole, considerable ingredients 
of plants. They are however the principal sources of the nitrogen of 
vegetation, and, serving as plant-food, enter plants through their roots, 
chiefly from the soil, and exist within them in small quantity, and for 
a time, pending the conversion of their nitrogen into that of the 
amides and albuminoids, to whose production they are probably 
essential. In seeds and fruits, and in mature plants, growing in soils 



114 HOW CROPS GROW. 

AVERAGE QUANTITY OF ALBUMINOIDS IN VARIOUS VEGETABLE 
PRODUCTS.— ALBUMINOIDS = N X 6.25. 

American, Jenkins. German, Wolff. 

Maize fodder, green 1.8 1.9 

Beet tops, " 2.7 3.0 

Carrot tops, " 4.3 5.1 

Meadow grass, in bloom 3.1 4.8 

Red clover, " • 3.7 4.8 

White clover, " 4.0 5.6 

Turnips, fresh 1.1 1-8 

Carrots, " 1.1 2.2 

Potatoes, « 2.2 3.4 

Corn cobs, air-dry 2.3 2.3 

Straw, " 3.5 4.0 

Pea straw, " 7.3 10.4 

Bean straw, « 10.2 16.3 

Meadow hay, in bloom 7.0 15.5 

Red-clover hay, " 12.5 19.7 

White-clover hay, " 14-6 23.2 

Buckwheat kernel, air-dry 10.0 14.4 

Barley " " 12.4 16.0 

Maize " " 10.6 16.0 

Rye " " 10.6 17.6 

Oat " " H.4 17.6 

Wheat " " 11.8 20.8 

Pea " " 22.4 35.8 

Bean " " 24.1 40.8 

The Amides, Amidoacids, Imides, and Amines. 
— Amrnonia and the ammonium salts, so important as 
food to plants, and as ingredients of the atmosphere, of 
soils, and of manures, occur in so small proportions in 
living vegetation as to scarcely require notice in this 
work occupied with the composition of Plants. They 
are, however, important in connection with the amides 
now to be briefly described. Ammonia, an invisible gas 
of pungent odor which dissolves abundantly in water to 
form the aqua ammonia of spirits of hartshorn of the 
apothecary, is a compound of one atom of nitrogen with 
three atoms of hydrogen. It unites to acids, forming 
the ammonium salts : 



of moderate fertility, both ammonia and nitric acid, or strictly speak- 
ing, ammonia-salts "and nitrates, commonly occur in very small pro- 
portions. In roots, stems, and foliage of plants situated in soils rich 
in these substances, they may be present in notable quantity. The 
dry leaves and stems of tobacco and beets sometimes contain several 
per cent of nitrates. When these substances are presented to plants in 
abundance, especially in dry weather, they may accumulate in the 
roots and lower parts "of the plant more rapidly than they can be assim- 
ilated. On the other hand, when their supply in the soil is relatively 
small they are so completely and rapidly assimilated as to be scarcely 
detectable. Their possible presence should be taken into account when 
it is undertaken to calculate the albuminoids of the plant from the 
amount of nitrogen found in its analysis. 



THE VOLATILE PART OF PLANTS. 115 

CHgCOOH -I- NH 3 = CH 3 COONH 4 

Acetic acid. Ammonia. Ammonium acetate. 

Amides. — This term is often used as a general desig- 
nation for all the bodies of this section which result from 
the substitution of the hydrogen of ammonia by any 
atom or group of atoms. In a narrower sense amides 
are those ammonia-derivatives containing "acid-radi- 
cals " which are indicated in their systematic names. 

Acetamide, CH 3 COKH 2 . Many ammonium salts, 
when somewhat strongly heated, suffer decomposition 
into amides and water. 

CH 3 C00XH 4 = CH 3 CONH 2 + H,0 

Ammonium acetate. Acetamide. Water. 

The above equation shows that acetamide is ammonia, 
NH 3 , or HNH 2 , one of whose hydrogens has been re- 
placed by the group of atoms, CH 3 CO, the acetic acid 
radical, so called. Acetamide is a white crystalline body. 
The simple amides, like acetamide, are as yet not known 
to exist in plants. They readily unite with water to 
produce ammonium salts. 

Carbamide, or Urea C0(]SrH2) 2 . This substance — 
the amide of carbonic acid CO(OH) 2 — naturally occurs 
in considerable proportion in the urine of man and mam- 
malian animals. It is a white, crystalline body, with a 
cooling, slightly salty taste, which readily takes up the 
elements of water and passes into ammonium carbonate. 
Urea has not been found in plants, but derivatives of it 
in which acid radicals replace a part of its hydrogen are 
of common occurrence. (Guanin, allantoin.) 

Amidoacids are acids containing the NH 2 group as a 
part of the acid radical. 

Amidoacetic Acid, 2 H 5 N0 2 , or CH 2 (NH 2 )COOH, 
is derived from acetic acid, CH 3 COOH, by the replace- 
ment of H in CH 3 by NH 2 . The amidoacids have not a 
sour, but usually a sweetish taste, and, like the amides, 
act both as weak acids and weak bases. Amidoacetic 



116 HOW CROPS GROW. 

acid, also called glycocoll, has not as yet been found in 
plants, but exists in the scallop and probably in other 
shell-fish, and a compound of it, benzoylglycocoll or hip- 
puric acid, is a nearly constant ingredient of the urine of 
the horse and other domestic herbivorous animals. 

Betain, or trimethylglycocoll, C 5 H n N0 2 , a crystalliza- 
ble substance found in beet-juice, stands in close chem- 
ical relations to amidoacetic acid. 

Amidovaleric acid, CsHnNOs, occurs in ox-pancreas 
and in young lupin plants. Amidocaproic acid, or 
Leucin, C 6 H 13 N0 2 , first observed in animals, has lately 
been discovered in various plants. The same is true 
of Tyrosin, or oxyphenyl-amidopropionic acid, 
CgHnNOs, and of phenyl - amidopropionic acid, 
C 9 H n N0 2 . 

The above amidoacids are readily obtained as products 
of decomposition of animal and vegetable albuminoids by 
the action of hot acids. Amidoacetic acid was thus first 
obtained from gelatin. Leucin and Tyrosin are com- 
monly prepared by boiling horn shavings with dilute sul- 
phuric acid ; they are also formed from vegetable albu- 
minoids by similar treatment and are final results of the 
digestion of proto- and deutero-proteoses (hemialbumose) 
under the action of trypsin and papain. 

Asparagin and Glutamin. — These bodies, which are 
found only in plants, are amides of amidoacids, being de- 
rived from dibasic acids. Asparagin, the amide of 
amidosuccinic acid, 

CH(NH 2 )COOH 
CH 2 CONH 2 

has been found in very many plants, especially in those 
just sprouted, as in asparagus, peas, beans, etc. Aspara- 
gin forms white, rhombic crystals, and is very soluble in 
water. 

Glutamin, the amide of amidoglutaric acid; 

C 3 H^H 2 , xCO()H - 



THE VOLATILE PART OF PLANTS. 117 

has been found, together with asparagin, in beet-juice 
and in squash seedlings. 

The amides, when heated with water alone, and more 
easily in presence of strong acids and alkalies, are con- 
verted into ammonia and the acids from which they are 
derived. Thus, asparagin yields ammonia and arnido- 
succinic acid at the boiling heat under the influence of 
hydrochloric acid, or of potassium hydroxide, and gluta- 
min is broken up by the last-named reagent at common 
temperatures, and by water alone at the boiling point, 
with formation of ammonia and amidoglutaric acid. 

The amidoacids are not decomposed by hot water or 
acids with separation of ammonia. Amidosuccinic and 
amidoglutaric acids result from albuminoids by boiling 
with dilute sulphuric acid, and by the action of bromine. 
The latter acid as yet has been obtained from vegetable 
albuminoids only, and is prepared most abundantly from 
gluten, and especially from mucedin. 

Imides, closely related to the amides, are a series of 
very interesting substances, into whose chemical consti- 
tution we cannot enter here further than to say that they 
contain several NH* groups, i. e., ammonia, NH 3 , in 
which two hydrogens are replaced by hydro-carbon, or 
oxycarbon groups or carbon atoms. 

These bodies are Uric acid, C 5 H 4 N 4 3 , Adcnin, C 5 H 5 N 5 , 
Guanin, C 5 H 5 N" 5 0, Allantoin, C 4 H 6 N 4 3 , Xantldn, 
Hypoxanthin, C 5 H 4 N 4 0, Theobromine C 7 H 8 4 2 , Caffein, 
C 8 HioN 4 2 , and Vernin, Ci 6 H 20 N 8 O 8 . Of these the 
first, so far as now known, occurs exclusively in the ani- 
mal. Adenin, Guanin, Allantoin, Xanthin, and Hypo- 
xanthin, are common to animals and plants ; the last 
three are exclusively vegetable. 

Caffein exists in coffee and tea combined with tannic 
acid. In the pure state it forms white, silky, fibrous 
crystals, and has a bitter taste. In coffee it is found to 

* Or its hydro-carbon derivatives. 



118 HOW CROPS GROW. 

the extent of one-half per cent ; in tea it occurs in much 
larger quantity, sometimes as high as 6 per cent. 

Theobromin resembles caffein in its characters. It 
is found in the cacao-bean, from which chocolate is man- 
ufactured. 

Vernin, discovered recently in various plants, young 
clover, vetches, squash-seedlings, etc., yields guanin by 
the action of hydrochloric acid. All these bodies stand 
in close chemical relations to each other, being complex 
imide derivatives of dioxymalonic (mesoxalic) acid. 

The amides and amidoacids, like ammonia, are able to 
combine directly with acids, are accordingly bases, but 
they are weak bases, because the basic quality of their 
ammonia is largely neutralized by the acid radicals already 
present in them. On the other hand, amides and ami- 
doacids often act as weak acids, for a portion of the hydro- 
gen of the NH 2 group is easily displaced by metals. 

The amides thus in fact possess in a degree the quali- 
ties of both the acid and of the base (ammonia) from 
which they are derived. They also are commonly "neu- 
tral" in the sense of having no sharp acid or alkaline 
taste or corrosive character. 

In vegetation amides appear as intermediate stages be- 
tween ammonium salts and albuminoids. They are, on 
the one hand, formed in growing plants from ammo- 
nium salts by a constructive process, and from them or 
by their aid, probably, the albuminoids are built up. On 
the other hand, in animal nutrition they are stages 
through which the elements of the albuminoids pass in 
their reversion to purely mineral matters. In germinat- 
ing seeds and developing buds they probably combine 
both these offices, being first formed in the germ from 
the albuminoids of the seed, entering the young plant or 
shoot, and in it being reconstructed into albuminoids. 
Their free solubility in water and ability to penetrate 
moist membranes adapt them for this movement. They 



THE VOLATILE PART OF PLANTS. 119 

temporarily accumulate in seedlings and buds, but disap- 
pear again as growth takes place, being converted into 
albuminoids, in which transformation they require the 
conjunction of carbhydrates. Their ability to unite with 
acid as well as bases further qualifies them to take part 
in these physiological processes. 

The imides are also at once weak bases and weak acids. 
Uric acid and allantoin, relatively rich in oxygen, have 
the acid qualities best developed. Guanin and caffein, 
with less oxygen and more hydrogen, are commonly 
classed among the organic bases, as in them the basic 
characters are most evident. 

Amines. — When the hydrogen of ammonia is replaced 
by hydrocarbon groups (radicals) such as Methyl, OH 3 , 
Ethyl, C 2 H 5 , Phenyl, C 6 H 5 , etc., compound ammonias or 
amines result which often resemble ammonia in physical 
and chemical characters, and some of them appear to be 
stronger bases than ammonia, being able to displace the 
latter from its combinations. 

Trimethylamine, N(CH 3 ) 3 , may be regarded as ammo- 
nia whose hydrogens are all substituted by the methyl 
group, CH 3 , and is a very volatile liquid having a rank, 
fishy odor, which may be obtained from herring pickle, and 
exhales from some plants, as from the foliage of Clienopo- 
dium vulvaria, and the flowers of Crataegus oxycantha. 
It is produced from tetain (trimethylamidoacetic acid), 
by heating with potash solution, just as ammonia is 
formed from many amides under similar treatment. 

Cholin, C 5 Hi 5 N0 2 , and Neurin, C 5 H 13 NO, are organic 
bases related to trimethylamine, which were first ob- 
tained from the animal. Cholin is an ingredient of the 
bile, and is found also in the brain and yolk of eggs, 
where it exists as a component of lecithin. It has latterly 
been discovered in the hop, lupin and pumpkin plants, 
and in cotton seed ; by oxidation it yields betain. Neu- 
rin is readily formed from cholin by the action of alka- 



120 HOW CROPS GROW. 

lies and in the process of putrefaction. It is a violent 
poison, and is perhaps one of the ingredients which, in 
the seeds of the vetch and of cotton, prove injurious, or 
even fatal, when these seeds are too largely eaten by ani- 
mals. Cholin and Neurin are syrupy, highly alkaline 
liquids. 

7. Alkaloids is the general designation that has 
been applied to the organic bases found in many plants, 
which are characterized in general by their poisonous 
and medicinal qualities. Caffein and Theobromin, already 
noticed, were formerly ranked as alkaloids. We may 
mention the following : 

Nicotin, Ci Hi 4 N 2 , is the narcotic and intensely poi- 
sonous principle in tobacco, where it exists in combina- 
tion with malic and citric acids. In the pure state it is 
a colorless, oily liquid, having the odor of tobacco in an 
extreme degree. It is inflammable and volatile, and so 
deadly that a single drop will kill a large dog. French 
tobacco contains 7 or 8 per cent ; Virginia, 6 or 7 per 
cent ; and Maryland and Havana, about 2 per cent of 
nicotin. Mcotin contains 17.3 per cent of nitrogen, 
but no oxygen. 

Lupinidin, C 8 H 15 N, Lupanin, Ci 5 H 25 N 2 0, and Lu~ 
pinin, C 2 iH 4 oN 2 2 , are bases existing in the seeds of the 
lupin. The first two are liquids ; the last is a crystal- 
line solid. They are poisonous and are believed to occa- 
sion the sickness which usually follows the use of lupin- 
seeds in cattle food. 

Sinapin, Ci 6 H 23 ]N"05, occurs in white mustard. When 
boiled with an alkali it is decomposed, yielding neurin 
as one product. 

Vicin, C 28 H 51 N n 2 i, and Convicin, C 10 H 14 NsO7, are 
crystalline bases that occur in the seeds of the vetch, with 
regard to whose nature and properties little is known. 

Avenin, C 56 H 21 ]SrOi 8 , according to Sanson, is a sub- 
stance of alkaloidal character, existing in oats. It is said 



THE VOLATILE PART OF PLANTS. 121 

to be more abundant in dark than in light -colored oats, 
and, when present to the extent of more than nine-tenths 
of one per cent, to act as a decided nerve-excitant on ani- 
mals fed mainly on oats. Avenin is described as a gran- 
ular, brown, non-crystallizable substance, but neither 
Osborne (at the Connecticut Experiment Station) nor 
"Wrampelmeyer (Vs. St., XXXVI, p. 299) have been able 
to find any evidence of the presence of such a body in oats. 

Morphin, Ci 7 H 19 N0 3 , occurs, together with several 
other alkaloids, in opium, the dried milky juice of the 
seed-vessels of the poppy cultivated in India. Its use in 
allaying pain and obtaining sleep and its abuse in the 
*' opium habit" are well known. 

Piperin, Ci 7 H 19 N0 3 , the active principle of white and 
black pepper, is a white crystalline body isomeric with 
morphin. 

Quinin, C 20 II 24 N 2 O 2 , is the most important of several 
bases used as anti-malarial remedies obtained from the 
bark of various species of cinchona growing in the forests 
of tropical South America, and cultivated in India. 

Strychnin, C 2 iH 22 N 2 2 , and Brucin, C 23 H 26 N 2 OH, is 
the intensely poisonous alkaloid of nux v-omica (dog 
button). 

Atropin, Ci 7 H 23 N0 3 , is the chief poisonous principle 
of the "Nightshade" or belladonna, and of stramonium 
or "Jamestown weed." 

Veratrin, C 32 H 49 N0 9 , is the chief toxic ingredient of 
the common White Hellebore, so much used as an 
insecticide. 

Solanin, C 42 H 87 N0 15 (?), is a poisonous crystalline 
alkaloid found in many species of Solanum, especially in 
the black nightshade (Solanum nigrum). It occurs in the 
sprouted tubers and green fruit of the potato (Solanum 
tuberosum) and in the stems and leaves of the tomato 
(Solanum ly coper sicum). 

The alkaloids, so far as investigated, appear to be more 



122 HOW CROPS GROW. 

or less complex derivatives of the bases Pyridin, C 5 H 5 N, 
and Quinolin, C 9 H 7 N, which are colorless, volatile 
liquids with sharp, unpleasant odor, produced from albu- 
minoids at high temperatures, and existing in smoke, 
bone-oil and tar. The alkaloids bear to these bases simi- 
lar relations to those subsisting between the amines and 
ammonia. 

8. Phosphorized Substances. — This class of bodies 
are important because of their obvious relations to the 
nutrition of the brain and nerve tissues of the animal, 
which have long been known to contain phosphorus as 
an essential ingredient. All our knowledge goes to show 
that phosphorus invariably exists in both plants and ani- 
mals as phosphoric acid or some derivative of this acid, 
or, in other words, that their phosphorus is always 
united to oxygen as in the phosphates, and is not directly 
combined to carbon, hydrogen, or nitrogen. 

Nuclein. — This term is currently employed to desig- 
nate various imperfectly-studied bodies that resemble the 
albuminoids in many respects, but contain several per 
cent of phosphorus. They are easily decomposable, 
boiling water being able to remove from them phosphoric 
acid, and under the action of dilute acids they mostly 
yield phosphoric acid, albuminoids and hypoxanthin, 
C5H4N4O, or similar imide bases. They are very difficult 
of digestion by the gastric juice. The nucleins are found 
in the protoplasm and especially in the cell-nuclei (see 
p. 245), of both plants and animals, and have been ob- 
tained from yeast, eggs, milk, etc., by a process based on 
their indigestibility by pepsin. Chemists are far from 
agreed as to the nature or composition of the nucleins. 

Lecithin, C44H 90 NPO 9 . — This name applies to a num- 
ber of substances that have been obtained from the brain 
and nerve tissue of animals, eggs and milk, as well as 
from yeast, and the seeds of maize, peas, and wheat. 
The lecithins are described as white, wax-like substances, 



THE VOLATILE PART OF PLANTS. 123 

imperfectly crystallizable, similar to protagon in their 
deportment toward water, and readily decomposed into 
cholin, glycerophosphoric acid, and one or more fatty 
acids. Three lecithins appear to have been identified, 
yielding respectively, on decomposition, stearic, palmitic, 
and oleic acids. 

The formula O44H90NPO9 is that of distearic lecithin, 

which is composed of glyceryl, C 3 H 5 , united to two 

stearic acid radicals, and also to phosphoric acid, which 

again is joined to cholin, as represented by the formula — 

/oc 18 h 35 o 

C 3 H 6 — OC lg H 3r ,0 

^OPO /OC 2 H 4 N(CH 3 ) 8 OH 

Lecithin is believed to be a constant and essential in- 
gredient of plants and animals. 

Protagon, CieoHgosNsPOgs, discovered by Liebreich in 
the brain of animals, has been further studied by Gam- 
gee & Blankenhorn. It is a white substance that swells 
up with water to a gelatinous mass and finally forms an 
opake solution. From solution in ether or alcohol it can 
be easily obtained in needle-shaped crystals, whose com- 
position is given below. Alkalies decompose protagon 
into glycero-phosphoric acid, stearic and other fatty 
acids, and cholin or neurin. Protagon was formerly 
confounded with lecithin and thought to exist in plants, 
but its presence in the latter has not been established. 

Protagon. Lecithin. 

Carbon G6.39 65.43 

Hydrogen 10.69 11.16 

Nitrogen 2.39 1.73 

Phosphorus 1.07 3.84 

Oxygen 19.46 17.84 

100.00 100.00 

Knop was the first to show that the crude fat which is 
extracted from plants by ether contains an admixture of 
some substance of which phosphorus is an ingredient. 
In the oil obtained from the sugar-pea he found 1.25 per 
cent, of phosphorus. Topler afterwards examined the 



124 HOW CROPS GROW. 

oils of a large number of seeds for phosphorus with the 
subjoined results : 

Source of Per cent, of I Source of Per cent, of 

fat. ' phosphorus. J fat. phosphorus. 

Lupin 0.29 i Walnut trace 

Pea 1-17 Olive none 

Horse-bean 0.72 Wheat 0.25 



Vetch 0.50 

Winter lentil 0.39 

Horse-chestnut 0.40 

Chocolate-bean none 

Millet " 

Poppy " 



Bailey 0.28 

Rye 0.31 

Oat 0.44 

Flax none 

Colza " 

Mustard " 



It is probable that the phosphorus in these oils existed 
in the seeds as lecithin, or as glycerophosphoric acid, 
which is produced in the decomposition of lecithin. Max- 
well (Constitution of the Legumes), reckoning from the 
phosphoric acid found in the ether-extract, estimates the 
pea kernel to contain 0.368 per cent, the horse-bean 
(Faba vulgaris) 0.600 per cent, and the vetch 0.532 per 
cent of lecithin. Lecithin is thus calculated to make up 
19.63 per cent of the crude fat of the pea, 31.54 per 
cent of the crude fat of the horse-bean, and 35.24 per 
cent of that of the vetch. 

Chlorophyl, i. e. , leaf -green, is the name applied to 
the substance which occasions the green color in vegeta- 
tion. It is found in all those parts of most annual plants 
and of the annually renewed parts of perennial plants 
which are exposed to light. The green parts of plants 
usually contain chlorophyl only near their surface, and 
in quantity not greater than one or two per cent of the 
fresh vegetable substance. 

Chlorophyl, being soluble in ether, accompanies fat or 
wax when these are removed from green vegetable mat- 
ters by this solvent. It is soluble in alcohol and hydro- 
chloric and sulphuric acids, imparting to these liquids an 
intense green color, but it suffers alteration and decom- 
position so readily that it is doubtful if the composition 
of chlorophyl, as it exists in the living leaf, is accurately 
known, especially since it is there mixed with other sub- 



THE VOLATILE PART OF PLANTS. 125 

stances, separation from which is difficult or imprac- 
ticable. 

Chlorophyllan, obtained by Hoppe-Seyler from grass, 
separates from its solution in hot alcohol in characteristic 
acicular crystals which are brown to transmitted light, 
and in reflected light are blackish green, with a velvety, 
somewhat metallic lustre. This substance has the con- 
sistence of beeswax, adheres firmly to glass, and at about 
230° melts to a brilliant black liquid. The crystallized 
chlorophyllan has a composition as follows : 

CHLOROPHYLLAN. 

Carbon 73.36 

Hydrogen 9.72 

Nitrogen 5.68 

Phosphorus 1.38 

Magnesium 0.34 

Oxygen 9.52 

100.00 

Chlorophyllan is chemically distinct from chlorophyl, 
as proved by its optical properties, but in what the dif- 
ference consists is not understood. Boiling alkali decom- 
poses it with formation of chlorophyllanic acid that 
may be obtained in blue-black crystals, and at the same 
time glycerophosphoric acid and cholin, the decomposi- 
tion-products of lecithin, are produced. Tschirch found 
that chlorophyllan, by treatment with zinc oxide, yields 
a substance w r hose optical properties lead to the belief 
that it is identical with the chlorophyl that occurs in the 
living plant. It was obtained as a dark-green powder, 
but its exact chemical composition is not known. 

The special interest of chlorophyl lies in the fact that 
it is to all appearance directly concerned in those con- 
structive processes by which the plant composes starch 
and other carbhyd rates out of the mineral substances 
which form its food. 

Xanthophyl is the yellow coloring matter of leaves 
and of many flowers. It occurs, together with chlorophyl, 
in green leaves, and after disappearance of chlorophyl 
remains as the principal pigment of autumn foliage. 



1^6 HOW CTiOPS GROW. 



CHAPTER II. 
THE ASH OF PLANTS. 

THE INGREDIENTS OF THE ASH. 

As has beeu stated, the volatile or destructible part of 
plants, i. e., the part which is converted into gases or 
vapors under the ordinary conditions of burning, con- 
sists chiefly of Carbon, Hydrogen, Oxygen and Nitro- 
gen, together with small quantities of Sulphur and Phos- 
phorus. These elements, and such of their compounds 
as are of general occurrence in agricultural plants, viz., 
the Organic Proximate Principles, have been already 
described in detail. 

The n on -volatile part or ash of plants also contains, 
or may contain, Carbon, Oxygen, Sulphur, and Phos- 
phorus. It is, however, in general, chiefly made up of 
eight other elements, whose common compounds are 
permanent at the ordinary heat of burning. 

In the subjoined table, the names of the 12 elements 
of the ash of plants are given, and they are grouped 
under two heads, the non-metals and the metals, by rea- 
son of an important distinction in their chemical nature. 

ELEMENTS OF THE ASH OF PLANTS. 

Xon-Mctals. ^^ctals. 

Oxygen. Potassium. 

Carbon. Sodium. 

Sulplmr. Calcium. 

Phosphorus. Magnesium. 

Silicon. Iron. 

Chlorine. Manganese. 

If to the above be added 

Hydrogen and Nitrogen 



THE ASH OF PLANTS. 127 

the list includes all the elementary substances that belong 
to agricultural vegetation. 

Hydrogen is never an ingredient of the perfectly 
burned and dry ash of any plant. 

Nitrogen may remain in the ash under certain con- 
ditions in the form of a Cyanide (compound of Carbon 
and Nitrogen), as will be noticed hereafter. 

Besides the above, certain other elements are found, either occasion- 
ally in common plants, or in some particular kind of vegetal ion ; these 
are Iodine, Bronflne, Fluorine, Titanium, Boron, Arsenic, Lithium, 
Rubidium, Barium, Aluminum, Zinc, Copper. These elements, how- 
ever, so far as known, have no special importance in agricultural 
chemistry, and mostly require no further notice. 

We may now complete our study of the Composition 
of the Plant by attending to a description of those ele- 
ments that are peculiar to the ash, and of those com- 
pounds which may occur in it. 

It will be convenient also to describe in this section 
some substances, which, although not ingredients of the 
ash, may exist in the plant, or are otherwise important 
to be considered. 

The Non-metallic Elements, which we shall first 
notice, though differing more or less widely among them- 
selves, have one point of resemblance, viz., they and their 
compounds with each other have acid properties, i. e., 
they either are acids in the ordinary sense of being sour 
to the taste, or enact the part of acids by uniting to met- 
als or metallic oxides to form salts. We may, therefore, 
designate them as the acid elements. They are Oxygen, 
Sulphur, Phosphorus, Carbon, Silicon, and Chlorine. 

With the exception of Silicon, and the denser forms of 
Carbon, these elements by themselves are readily volatiK 
Their compounds with each other, which may occur in 
vegetation, are also volatile, with two exceptions, viz., 
Silicic and Phosphoric acids. 

In order that they may resist the high temperature at 
which ashes are formed, they must be combined with the 
metallic elements or their oxides as salts. 



128 HOW CROPS GROW. 

Oxygen, Symbol 0, atomic iveight 16, is an ingredient 
of the ash, since it unites with nearly all the other ele- 
ments of vegetation, either during the life of the plant, 
or in the act of combustion. It unites with Carbon, 
Sulphur, Phosphorus, and Silicon, forming acid bodies ; 
while with the metals it produces oxides, which ha\e the 
characters of bases. Chlorine alone of the elements of 
the plant does not unite with oxygen, either in the living 
plant, or during its combustion. 

CARBON AND ITS COMPOUNDS. 

Carbon, Sym. C, at. wt. 12, has been noticed already 
with sufficient fullness (p. 14). It is often contained as 
charcoal in the ashes of the plant, owing to its being en- 
veloped in a coating of fused saline matters, which shield 
it from the action of oxygen. 

Carbon Dioxide, commonly termed Carbonic acid, 
Sym. 00 2 , molecular weight 44, is the colorless gas 
which causes the sparkling or effervescence of beer and 
soda water, and the frothing of yeast. 

It is formed by the oxidation of carbon, when vegeta- 
ble matter is burned (Exp. 6). It is, therefore, found 
in the ash of plants, combined with those bases which in 
the living organism existed in union with organic acids ; 
the latter being destroyed by burning. 

It also occurs in combination with calcium in the tissues 
of many plants. Its compounds with bases are carbon- 
ates, to be noticed presently. When a carbonate, as mar- 
ble or limestone, is drenched with a strong acid, like 
vinegar or muriatic acid, the carbon dioxide is set free 
with effervescence. 

Carbonic Acid, H 2 C0 3 , or CO(OH) 2 , mo. tot. 62. 
This, the carbonic acid of modern chemistry, is not known 
as a distinct substance, since, when set free from carbon- 
ates by the action of a stronger acid, it falls into carbon 
dioxide and water : 



THE ASH OF PLANTS. 129 

CaC0 3 -j- 2 HC1 = CaCl, -+- H 2 C0 3 and H 2 C0 3 = H,0 + CO r 

Carbon dioxide is also termed anhydrous carbonic acid, 
or again, carbonic anhydride. 

CYANOGEN, Sym. C S N 8 . — This important compound of Carbon and Ni- 
trogen is a gas which has an odor like that of peach-pits, and which 
burns on contact with a lighted taper with a fine purple flame. In its 
union with oxygen by combustion, carbon dioxide is formed, and nitro- 
gen set free : 

C 2 N 2 + 4 O = 2 C0 2 + No. * 

Cyanogen may be prepared by heating an intimate mixture of two 
parts by weight of ferrocyanide of potassium (yellow prussiate of 
potash) and three parts of corrosive sublimate. The operation may 
be conducted in a test-tube or small flask, to the mouth of which is 
fitted a cork penetrated by a narrow.glass tube. On applying heat, the 
gas issues, and may be set on fire to observe its beautiful flame. 

Cyanogen, combined with iron, forms the Prussian blue of com- 
merce, and its name, signifying the blue-producer, was given to it from 
that circumstance. 

Cyanogen unites with the metallic elements, giving rise to a series 
of bodies which are termed Cyanides. Some of these often occur in 
small quantity in the ashes of plants, being produced in the act of 
burning by the union of nitrogen with carbon and a metal. For this 
result, the temperature must be very high, carbon must be in excess, 
the metal is usually potassium or calcium, the nitrogen may be either 
free nitrogen of the atmosphere or that originally existing in the 
organic matter. 

"With hydrogen, cyanogen forms the deadly poison hydrocyanic or 
prussic acid, HCy, which is produced from amygdalin, one of the ingre- 
dients of bitter almonds, peach, and cherry seeds, when these are 
crashed in contact with water. 

"When a cyanide is brought in contact with steam at high tempera- 
tures, it is decomposed, all its nitrogen being converted into ammonia. 

Cyanogen is a normal ingredient of one common plant. The oil of 
mustard is aUylsulphocyanate, C 8 H 5 CNS. 

SULPHUR AND ITS COMPOUNDS. 

Sulphur, Sym. S, at. wt. 32. — The properties of this 
element have been already described (p. 25). Some of 
its compounds have also been briefly alluded to, but re- 
quire more detailed notice. 

Hydrogen Sulphide, Sym. H,S, mo. wt. 34. This substance, familiarly 
known as sulphuretted hydrogen, occurs dissolved in the water of nu- 
merous so-called sulphur springs, as those of Avon and Sharon, N. Y., 
from which it escapes as a fetid gas. It is not unfrequently emitted 
from volcanoes and fumaroles. It is likewise produced in the decay of 
organic bodies which contain sulphur, especially eggs, the intolerable 
odor of which, when rotten, is largely due to this gas. It is evolved 
from manure heaps, from salt marshes, and even from the soil of moist 
meadows. 

9 



130 HOW CROPS CROW. 

The ashes of plants sometimes yield this gas when they are moistened 
with water. In such cases, a sulphide of potassium or calcium has been 
formed in small quantity during the incineration. 

Hydrogen Sulphide is set free in the gaseous form "by the action of an 
acid on various sulphides, as those of iron (Exp. 17), antimony, etc., as 
well as by the action of water on the sulphides of the alkali and alkali- 
earth metals. It may be also generated by passing hydrogen gas into 
melted sulphur. 

Sulphuretted hydrogen has a slight acid taste. It is highly poisonous 
and destructive, both to animals and plants. 

Sulphur Dioxide, commonly called Sulphurous Acid, Sym. SO,, mo. 
wt. G4. When sulphur is burned in the air, or in oxygen gas, it forms 
copious white suffocating fumes, which consist of one atom of sulphur, 
united to two atoms of oxygen ; S0 2 (Exp. 15). 

Sulphur dioxide is characterized by its power of discharging, for a 
time at least, most of the red and*blue vegetable colors. It has, how- 
ever, no action on many yellow colors. Straw and wool are bleached 
by it in the arts. 

Sulphur dioxide is emitted from volcanoes, and from fissures in the 
soil of volcanic regions. It is produced when bodies containing sul- 
phur are burned with imperfect access of air, and is thrown into the 
atmosphere in large quantities from fires which are fed by mineral 
coal, as well as from the numerous roasting heaps of certain metallic 
ores (sulphides) which are wrought in mining regions. 

Sulphur dioxide may unite with bases, yielding salts known as sul- 
phites, some of which, viz., calcium sulphite and sodium sulphite, are 
employed to check or prevent fermentation, an effect also produced by 
the acid itself. 

Sulphur-Trioxide, Sym. S0 3 , mo. wt. 80, is known 
to the chemist as a white, silky solid, which attracts 
moisture with great avidity, and, when thrown into 
water, hisses like a hot iron, forming sulphuric acid. 
Sulphur trioxide was formerly termed sulphuric acid or 
anhydrous sulphuric acid, and now it is common in 
statements of analysis to follow this usage. 

Sulphuric Acid, Sym. H 2 S0 4 , mo. wt. 98, is a sub- 
stance of the highest importance, its manufacture being 
the basis of the chemical arts. In its concentrated form 
it is known as oil of vitriol, and is a colorless, heavy 
liquid, of an oily consistency, and sharp, sour taste. 

It is manufactured on the large scale by mingling sul- 
phur dioxide gas, nitric acid gas, and steam, in large 
lead-lined chambers, the floors of which are covered with 
water. The sulphur dioxide takes up oxygen from the 



THE ASH OF PLANTS. 131 

nitric acid, and the sulphuric acid thus formed dissolves 
in the water, and is afterwards boiled down to the proper 
strength in glass vessels. 

The chief agricultural application of sulphuric acid is 
in the preparation of " superphosphate of lime," which 
is consumed as a fertilizer in immense quantities. This 
is made by mixing together sulphuric acid, somewhat 
diluted with water, with bone-dust, bone-ash, or some 
mineral phosphate. Commercial oil of vitriol is a mix- 
ture of sulphuric acid with more or less water. The 
strongest oil of vitriol commonly made, or "66° acid," 
contains 93.5% of H 2 S0 4 . The so-called "60° acid" 
contains 77.6% II 2 S0 4 or 83% of 66° acid. Chamber 
acid or "51° acid" contains 63.6% H 2 S0 4 , or 67% of 
66° acid. 

Sulphuric acid occurs in the free state, though ex- 
tremely dilute, in certain natural waters, as in the Oak 
Orchard Acid Spring of Orleans, N. Y., where it is pro- 
duced by the oxidation of sulphide of iron. 

Sulphuric acid is very corrosive and destructive to most 
vegetable and animal matters. 

Exp. 53.— Stir a little oil of vitriol with a pine stick. The wood is im- 
mediately browned or blackened, and a portion of it dissolves in the 
acid, communicating a dark color to the latter. The commercial acid 
is often brown from contact with straws and chips. 

Strong sulphuric acid produces great heat when mixed with water, 
as is done for making superphosphate. 

Exp. 54. — Place in a thin glass vessel, as a beaker glass, 30 c. c. of water ; 
into this pour in a fine stream 120 grams of oil of vitriol, stirring all the 
while with a narrow test-tube, containing a teaspoonful of water. If the 
acid be of full strength, so much heat is thus generated as to boil the 
water in tlie stirring tube. 

In mixing oil of vitriol and water, the acid should always be slowly 
poured into the water, with* stirring, as above directed. When water 
is added to the acid, it floats upon the latter, or mixes with it but super- 
ficially, and the liquids may be thrown about by the sudden formation 
of steam at the points of contact, when subsequently stirred. 

Sulphuric acid forms with the bases an important class 
of salts — the sulphates, to be presently noticed — some of 
which exist in the ash, as well as in the sap of plants. 



132 HOW CROPS GROW. 

When organic matters containing sulphur — as hair, 
albumin, etc. — are burned with full access of air, this 
element remains in the ash as sulphates, or is partially 
dissipated as sulphur dioxide. 

IHOSPHORUS AND ITS COMPOUNDS. 

Phosphorus, Sym. P, at. wt. 31, has been sufficiently 
described (p. 27). Of its numerous compounds but two 
require additional notice. 

Phosphorus Pentoxide, Sym. P 2 5 , mo. wt. 142, 
does not occur as such in nature. When phosphorus is 
burned in dry air or oxygen, anhydrous phosphoric acid 
is the snow-like product (Exp. 18). The term "phos- 
phoric acid," as now encountered in fertilizer analyses, 
has reference to ''anhydrous phosphoric acid," as phos- 
phorus pentoxide was formerly designated. Phosphorus 
pentoxide has no sensible acid properties until it has 
united to water, which it combines with so energetically 
as to produce a hissing noise from the heat developed. 
On boiling it with water for some time, it completely dis- 
solves, and the solution contains — 

Phosphoric Acid, Sym. H 3 P0 4 , 98.— The chief in- 
terest which this compound has for the agriculturist lies 
in the fact that the combinations which are formed be- 
tween it and various bases— phosphates — are among the 
most important ingredients of plants and their ashes. 

When organic bodies containing phosphorus, as le- 
cithin (p. 122), and, perhaps, some of the albuminoids, 
are decomposed by heat or decay, the phosphorus appears 
in the ashes or residue, in the condition of phosphoric 
acid or phosphates. 

The formation of several phosphates has been shown in 
Exp. 20. Further account of them will be given under 
the metals. 

CHLORINE AND ITS COMPOUNDS. 

' Chlorine, Sym. CI., at. wt. 35.5. — This element exists 



THE ASH OF PLANTS. 133 

in the free state as a greenish-yellow, suffocating gas, 
which has a peculiar odor, and the property of bleaching 
vegetable colors. It is endowed with the most vigorous 
affinities for many other elements, and hence is never met 
with, naturally, in the free state. 

Exp. 55.— Chlorine may be prepared by heating a mixture of hydro- 
chloric acid and black oxide of manganese or red-lead. The gas being 
nearly live times as heavy as common air, may be collected in glass 
bottles by passing the tube which delivers it to the bottom of the re- 
ceiving vessel. Care must be taken not to inhale it, as it energetically 
attacks the interior of the breathing passages, producing the disagree- 
able symptoms of a cold. 

Chlorine dissolves in water, forming a yellow solution. 

In some form of combination chlorine is distributed 
over the whole earth, and is never absent from the plant. 

The compounds of chlorine are termed chlorides, and 
may be prepared, in most cases, by simply putting their 
elements in contact, at ordinary or slightly elevated tem- 
peratures. 

Hydrochloric Acid, Sym. HC1, mo. wt. 36.5.— When Chlorine and 
Hydrogen gases are mingled together, they slowly combine if exposed 
to diffused light ; but if placed in the sunshine, they unite explosively, 
and hydrogen chloride or hydrochloric acid is formed. This compound 
is a gas that dissolves with great avidity in water, forming a liquid 
which has a sharp, sour taste, and possesses all the characters of an 
acid. 

The muriatic acid of the apothecary is water holding in solution 
several hundred times its bulk of hydrochloric acid gas, and is pre- 
pared from common salt, whence its ancient name, spirits of salt. 

Hydrochloric acid is the usual source of chlorine gas. The latter is 
evolved from a heated mixture of this acid with black oxide of manga- 
nese. In this reaction hydrogen of the hydrochloric acid unites 
with oxygen of the oxide of manganese, producing water, while 
chloride of manganese and free chlorine are separated. 

4 HC1 + Mn0 2 = MnCl 2 + 2 H, O + 2 CI. 
When chlorine, dissolved in water, is exposed to the sunlight, there 
ensues a change the reverse of that just noticed. Water is decom- 
posed, its oxygen is set free, and hydrochloric acid is formed. 

H 2 -(- 2 Cl= 2 HC1 -(- O. 

The two reactions just noticed are instructive examples of the differ- 
ent play of affinities between several elements under unlike circum- 
stances. 

This acid is a ready means of converting various metals or metallic 
oxides into chlorides, and its solution in water is a valuable solvent 
and reagent for the purpose of the chemist. 



134 HOW CROPS GROW. 

Iodine, Sym. I, at. wt. 127.— This interesting body is a black solid at 
ordinary temperatures, having an odor resembling that of chlorine. 
Gently heated, it is converted into a violet vapor. It occurs in sea- 
weeds, and is obtained from their ashes. It gives with starch a blue or 
purple compound, and is hence employed as a test for that substance 
(p 49). It is analogous to chlorine in its chemical relations. It is not 
knoAvn to occur in sensible quantity in agricultural plants, although it 
may well exist in the grasses of salt-bogs, and in the produce of soils 
which are manured with sea-weed. 

Bromine and Fluorine may also exist in very small quantity in 
plants, but these elements require no further notice in this treatise. 

SILICON" AND ITS COMPOUNDS. 

Silicon, Sym. Si, at. wt. 28. — This element, in the 
free state, is only known to the chemist. It may be pre- 
pared in three modifications : one, a brown, powdery 
substance ; another, resembling plnmbago, and a third, 
that occurs in crystals, having the form and nearly the 
hardness of the diamond. 

Silicon Dioxide, Sym. Si0 2 , mo. wt. 60. — This com- 
pound, known also as Silica, is widely diffused in nature, 
and occurs to an enormous extent in rocks and soils, both 
in the free state and in combination with other bodies. 

Free silica exists in nearly all soils, and in many rocks, 
especially in sandstones and granites, in the form known 
to mineralogists as quartz. The glassy, white, or trans- 
parent, often yellowish or red, fragments of common sand, 
which are hard enough to scratch glass, are almost inva- 
riably this mineral. In the purest state, it is rock-crys- 
tal. Jasper, flint, and agate are somewhat less pure 
silica. 

Silicates. — Silica is extremely insoluble in pure water 
and in most acids. It has, therefore, none of the sensi- 
ble qualities of acids, but is nevertheless capable of union 
with bases. It is slowly dissolved by strong, and espe- 
cially by hot, solutions of potash and soda, forming sol- 
uble- silicates of the alkali metals. 

Exp. 56.— Formation of potassium silicate. Heat a piece of quartz or 
flint, as large as a chestnut, as hot as possible in the fire, and quench 
suddenly in cold water. Reduce it to fine powder in a porcelain mor- 
tar, and boil it in a porcelain dish with twice its weight of caustic pot- 



THE ASH OF PLANTS. 135 

ash, and eight, or ten times as much water, for two hours, taking care 
to supply the water as it evaporates. Pour off the whole into a tall 
narrow bottle, and leave at rest until the undissolved silica has settled. 
The clear liquid is a basic potassium silicate, i. e., a silicate which con. 
tains a number of molecules of base for each molecule of silica. It 
has, in fact, the taste and feel of potash solution. The so-called water- 
glass, now employed in the arts, is a similar sodium silicate. 

When silica is strongly heated with potash or soda, or 
with lime, magnesia, or oxide of iron, it readily melts to- 
gether and unites with these bodies, though nearly infus- 
ible by itself, and silicates are the result. The silicates 
thus formed with potash and soda are soluble in water, 
like the product of Exp. 56, when the alkali exceeds a 
certain proportion — when highly basic ; but, with silica 
in excess (acid silicates), they dissolve with difficulty. 
A mixed silicate of sodium, calcium, and aluminum, with 
a large proportion of silica, is nearly or altogether insol- 
uble, not only in water, but in most acids — constitutes, 
in fact, ordinary glass. 

A multitude of silicates exist in nature as rocks and 
minerals. Ordinary clay, common slate, soapstone, mica, 
or mineral isinglass, feldspar, hornblende, garnet, and 
other compounds of frequent and abundant occurrence, 
are silicates. The natural silicates may be roughly dis- 
tinguished as belonging to two classes, viz., the acid sil- 
icates (containing a preponderance of silica) and basic 
silicates (with large proportion of base). The former are 
but slowly dissolved or decomposed by acids, while the 
latter are readily attacked, even by carbon dioxide acid. 
Many native silicates are anhydrous, or destitute of 
water ; others are hydrous, i. e., they contain water as a 
large and essential ingredient. 

The Silicic Acids. — Various silicic acids — compounds 
of silica with water — are known to the chemist, or are 
represented by the silicates found in nature. The silicic 
acids themselves have little stability and are readily re- 
solved into water and silica. 

Soluble Silica, Si(OH) 4 ? — This body is known only in 



136 now CROPS GROW. 

solution. It is formed when the solution of an alkali- 
silicate is decomposed by means of a large excess of some 
strong acid, like the hydrochloric or sulphuric. 

Exp. 57.— Dilute half the solution of potassium silicate obtained in 
Exp. 56 with ten times its volume of water, and add diluted hydrochloric 
acid gradually until the liquid tastes sour. In this Exp. the hydrochlo- 
ric acid decomposes and destroys the potassium silicate, uniting itself 
to the base with production of chloride of potassium, which dis- 
solves in the water present. The silica thus liberated unites chemi- 
cally with water, and remains also in solution. 

By appropriate methods Doveri and Graham have 
obtained solutions of silica in pure water. Graham pre- 
pared a liquid that gave, when evaporated and heated, 
14 per cent of anhydrous silica. This solution was clear, 
colorless, and not viscid. It reddened litmus-paper like 
an acid. Though not sour to the taste, it produced a 
peculiar feeling on the tongue. Evaporated to dryness at 
a low temperature, it left a transparent, glassy mass, 
which bad the composition H 2 Si0 3 . This dry residue 
was insoluble in water. These solutions of silica in pure 
water are incapable of existing for a long time without 
suffering a remarkable change. Even when protected 
as much as possible from all external agencies, they 
sooner or later, usually in a few days or weeks, lose their 
fluidity and transparency, and coagulate to a stiff jelly, 
from the separation of a nearly insoluble hydrate of silica, 
which we shall designate as gelatinous silica. 

The addition of too"<to °f an alkali or earthy carbon- 
ate, or of a few bubbles of carbon dioxide gas to the strong 
solutions, occasions their immediate gelatinization. A 
minute quantity of potash or soda, or excess of hydro- 
chloric acid, prevents their coagulation. 

Gelatinous Silica. — This substance, which results 
from the coagulation of the soluble silica just described, 
usually appears also when the strong solution of a silicate 
has strong hydrochloric acid added to it, or when a sili- 
cate is decomposed by direct treatment with a concen- 
trated acid. 



THE ASH OF PLANTS. 137 

It is a white, opaline, or transparent jelly, which, on 
drying in the air, becomes a fine, white powder, or forms 
transparent grains. This powder, if dried at ordinary 
temperatures, has a composition nearly corresponding to 
the formula H 4 Si 3 8 , or to a compound of 3 Si0 2 with 
2 H 2 0. At the temperature of 212° F., it loses half its 
water. At a red heat it becomes anhydrous. 

Gelatinous silica is distinctly, though very slightly, 
soluble in water. Fuchs and Bresser have found by ex- 
periment that 100,000 parts of water dissolve 13 to 14 
parts of gelatinous silica. 

The hydrates of silica which have been subjected to a 
heat of 212°, or more, appear to be totally insoluble in 
pure water. 

These hydrates of silica are readily soluble in solutions 
of the alkalies and alkali carbonates, and readily unite 
with moist, slaked lime, forming silicates. 

Exp. 58.— Gelatinous Silica.— Pour a small portion of the solution of 
silicate potassium of Exp. 56 into strong hydrochloric acid. Gelatinous 
silica separates and falls to the bottom, or the whole liquid becomes a 
transparent jelly. 

Exp. 59.— Conversion of soluble into insoluble hydrated silica.— Evapo- 
rate the solution of silica of Exp. 57, which contains free hydrochloric 
acid, in a porcelain dish. As it becomes concentrated, it is very likely 
to gelatinize, as happened in Exp. 58, on account of the removal of the 
solvent. Evaporate to perfect dryness, finally on a water-bath (i. e., on 
a vessel of boiling water which is covered by the dish containing the 
solution). Add to the residue water, which dissolves away the chlo- 
ride of potassium, and leaves insoluble hydrated silica, 3 Si0 2 H 2 0, as 
a gritty powder. 

Iii the ash of plants, silica is usually found in com- 
bination with alkali-metals or calcium, owing to the 
high temperature to which it has been subjected. 

In the plant, however, it exists chiefly, if not entirely, 
in the free state. 

Titanium, an element which has many analogies with silicon, though 
rarely occurring in large quantities, is yet often present in the form 
of Titanic acid,Ti0 2 , in rocks and soils, and, according to Salm-Horst- 
mar, may exist in the ashes of barley and oats. 

Arsexic, in minute quantity, was found by Davy in turnips which 
had been manured with a fertilizer (superphosphate), in whose prep- 
aration arsenical oil of vitriol was employed. 



138 HOW CROPS GROW. 

When arsenic, in the form of Paris green or London purple, is applied 
to land the arsenic soon becomes converted into highly insoluble iron 
compounds and is not taken up by plants in appreciable quantity. 

The Metallic Elements which remain to be noticed, 
viz.: Potassium, Sodium, Calcium, Magnesium, Iron, 
Manganese, Aluminium, Zinc, and Copper, are basic in 
their character, i. e., they unite with the acid bodies 
that have just been described, to produce salts. Each 
one is, in this sense, the base of a series of saline com- 
pounds. 

Alkali-metals. — The elements Potassium and Sodium 
are termed alkali-metals. Their oxides dissolve in and 
chemically unite to water, forming hydroxides that are 
called alkalies. The metals themselves do not occur in 
nature, and can only be prepared by tedious chemical 
processes. They are silvery-white bodies, and are lighter 
than ivater. Exposed to the air, they quickly tarnish 
from the absorption of oxygen and moisture, and are 
rapidly converted into the corresponding alkalies. 
Thrown upon water, they mostly inflame and burn with 
great violence, decomposing the liquid. Exp. 11. 

Of the alkali-metals, Potassium is invariably found in 
all plants. Sodium is especially abundant in marine and 
strand vegetation ; it is generally found in agricultural 
plants, but is sometimes present in them in but small 
quantity. 

POTASSIUM AND ITS COMPOUNDS. 

Potassium, Sym. K ; * at. wt. 39. — When heated in 
the air, this metal burns with a beautiful violet light, 
and forms potassium oxide. 

Potassium Oxide, or Potash, K 2 0, 94, is the so- 
called ''actual potash " that figures in the analyses of 
plants and valuation of fertilizers. It is, however, scarcely 
known as a substance, because it energetically unites 
with water and forms hydroxide. 

* From the Latin name Kolium. 



THE ASH OF PLANTS. 139 

Potassium Hydroxide, KOH, 56, is the caustic 
potash of the apothecary and chemist. It may be pro- 
cured in white, opaque masses or sticks, which rapidly 
absorb moisture and carbonic acid from the air, and 
readily dissolve in water, forming potash-lye. It strongly 
corrodes many vegetable and most animal matters, and 
dissolves fats, forming potash-soaps. Both the oxide 
and hydroxide of potassium unite to acids forming salts. 

SODIUM AND ITS COMPOUNDS. 

Sodium, Na,* 23. — Burns with a brilliant, orange- 
yellow flame, yielding sodium oxide. 

Sodium Oxide, or Soda, Na 2 0, 62, is practically lit- 
tle known, though constantly referred to as the base of 
the sodium salts. It unites to water, producing the hy- 
droxide. 

Sodium Hydroxide, or Caustic Soda, NaOH, 40. — 
This body is like caustic potash in appearance and gen- 
eral characters. It forms soaps with the various fats. 
AVhile the potash-soaps are usually soft, those made with 
soda are commonly hard. 

Alkali-earth Metals. — The two metallic elements 
next to be noticed, viz., Calcium and Magnesium, give, 
with oxygen, the alkali-earths, lime and magnesia. The 
metals are only procurable by difficult chemical pro- 
cesses, and from their eminent oxidability are not found 
in nature. They are but a little heavier than water. 
Their oxides are but slightly soluble in water. 

CALCIUM AND ITS COMPOUNDS. 

Calcium, Oa, 40, is a brilliant ductile metal having a 
light yellow color. In moist air it rapidly tarnishes and 
acquires a coating of lime. 

Calcium Oxide, or Lime, CaO, 56, is the result 



* From the Latin namo Natrium. 



140 HOW CROPS GROW. 

of the oxidation of calcium. It is prepared for use 
in the arts by subjecting limestone or oyster-shells to an 
intense heat, and usually retains the form and much of 
the hardness of the material from which it is made. It 
has the bitter taste and corroding properties of the alka- 
lies, though in a less degree. It is often called quick- 
lime, to distinguish it from its compound with water. 
It may occur in the ashes of plants when they have been 
maintained at a high heat after the volatile matter has 
been burned away. 

Calcium Hydroxide, Ca (OH) 2 , 74. — Quick-lime, 
when exposed to the air, gradually absorbs water and 
falls to a fine powder. It is then said to be air-slacked. 
When water is poured upon quick-lime it penetrates the 
pores of the latter, and shortly the falling to powder of 
the lime and the development of much heat give evi- 
dence of chemical union between the lime and the water. 
This chemical combination is further proved by the in- 
crease of weight of the lime, 56 lbs. of quick-lime becom- 
ing 74 lbs. by luater-slaching. On heating slacked lime 
to redness, water is expelled, and calcium oxide remains. 

When lime is agitated for some time with much water, 
and the mixture is allowed to settle, the clear liquid is 
found to contain a small amount of lime in solution (one 
part of lime to 700 parts of water). This liquid is called 
lime-tcater, and has already been noticed as a test, for 
carbonic acid. * Lime-water' has the alkaline taste in a 
marked degree. 

MAGNESIUM AND ITS COMPOUNDS. 

Magnesium, Mg, 24. — Metallic magnesium has a sil- 
ver-white color. When heated in the air ft burns with 
extreme brilliancy (magnesium light), and is converted 
into magnesia. 

Magnesium Oxide, or Magnesia, MgO, 40, is found 
in the drug-stores in the shape of a bulky white powder, 



THE ASH OF PLANTS. 141 

under the name of calcined magnesia. It is prepared by 
subjecting either magnesium hydroxide, carbonate, or 
nitrate, to a strong heat. It occurs in the ashes of 
plants. 

Magnesium Hydroxide, Mg(OH) 2 , is produced 
slowly and without heat, when magnesia is mixed with 
water. It occurs rarely as a transparent, glassy mineral 
(Brucite) at Texas, Pa., Hoboken, N. J., and a few 
other places. It readily absorbs carbon dioxide and passes 
into carbonate of magnesium. Magnesium hydroxide is 
so slightly soluble in water as to be tasteless. It requires 
55,000 times its weight of water for solution (Fresenius). 

Heavy Metals. — The two metals remaining to notice 
are Iron and Manganese. These again considerably re- 
semble each other, though they differ exceedingly from 
the metals of the alkalies and alkali-earths. They are 
about eight times heavier than water. Each of these 
metals forms two basic oxides, which are commonly 
insoluble in pure water. 

IRON AND ITS COMPOUNDS. 

Iron, Fe,* 56. — The properties of metallic iron are so 
well known that we need not occupy any space in reca- 
pitulating them. 

Ferrous Oxide, or Protoxide of Iron, FeO, 72. — 
When sulphuric acid in a diluted state is put in contact 
with metallic iron, hydrogen gas shortly begins to escape 
in bubbles from the liquid, and the iron dissolves, unit- 
ing with the acid to form ferrous sulphate, the salt 
known commonly as copperas or green-vitriol. 

H 2 S0 4 , + Fe = FeS0 4 + H 2 . 

If, now, lime-water or potash-lye be added to the solu- 
tion of iron thus obtained, a white or greenish w r hite pre- 
cipitate separates, which is ferrous hydroxide, Fe(OH) 2 . 

*From the Latin name Ferrum. 



142 HOW CEOPS GROW. 

This precipitate rapidly absorbs oxygen from the air, be- 
coming black and finally brown. The anhydrous pro- 
toxide of iron is black. Carbonate of protoxide of iron 
is of frequent occurrence as a mineral (spathic iron), and 
exists dissolved in many mineral waters, especially in 
the so-called chalybeates. The ferrous salts are mostly 
white or green. 

Ferric Oxide, or Peroxide of Iron, Fe 2 3 , 160. — 
When ferrous hydroxide is exposed to the air, it acquires 
a brown color from union with more oxygen, and becomes 
ferric hydroxide Fe(OH) 3 . The yellow or brown rust 
which forms on surfaces of metallic iron when exposed to 
moist air is the same body. Ferric oxide is found in 
the ashes of all agricultural plants, the other oxides of 
iron passing into this when exposed to air at high tem- 
peratures. It is found in immense beds in the earth, 
and is an important ore (specular iron, haematite). It 
dissolves in acids, forming the ferric salts, which have 
a yellow color. 

Magnetic Oxide of Iron, Fe 3 4 , or Fe0.Fe 2 3 , is a combination 
of the two oxides above mentioned. It is black, and is strongly at- 
tracted by the magnet. It constitutes, in fact, the native magnet, or 
loadstone, and is a valuable ore of iron. 

Manganese and its Compounds. 

Manganese, Mn, 55. — Metallic manganese is difficult 
to procure in the free state, and much resembles iron. 
Its oxides are analogous to those of iron just noticed. 

Manganous Oxide, or Protoxide of Manganese, 
MnO, 71, has an olive-green color. It is the base of all 
the usually occurring salts of manganese. Its hydrox- 
ide, prepared by decomposing manganous sulphate by 
lime-water, is a white substance, which, on exposure to 
the air, shortly becomes brown and finally black from 
absorption of oxygen. The manganous salts are mostly 
pale rose-red in color. 

Manganic Oxide, Mn 2 3 , occurs native as the mineral brmmite, or, 



THE ASH OF PLANTS. 143 

combined with water, as manganite. It is a substance having a red or 
black-brown color. It dissolves in cold acids, forming salts of an in- 
tensely red color. These are, however, easily decomposed by heat, or 
by organic bodies, into oxygen and manganous salts. 

Red Oxide of Manganese, Mn 3 4 , or MnO . Mn 2 3 .— This oxide re- 
mains when manganese or any of its other oxides are subjected to a 
high temperature with access of air. The metal and the protoxide 
gain oxygen by this treatment, the higher oxides lose oxygen until 
this compound oxide is formed, which, as its symbol shows, corres- 
ponds to the magnetic oxide of iron. It is found in the ashes of plants. 

Black Oxide of Manganese, Mn0 2 .— This body is found extensively 
in nature. It is employed in the preparation of oxygen and chlorine 
(bleaching powder), and is an article of commerce. 

Some other metals occur as oxides or salts in ashes, though not in 
such quantity or in such plants as to possess any agricultural signifi- 
cance in this respect. 

Alumina, A1 2 3 , the oxide of the metal Aluminium, is found in 
considerable quantity (20 to 50 per cent) in the ashes of the ground pine 
{Lycopodium). It is united with an organic acid {tartaric, according to 
Berzelius ; vialic, according to Ritthausen) in the plant itself. It is 
often found in small quantity in the ashes of agricultural plants, but 
whether an ingredient of the plant or due to particles of adhering clay 
is not in all cases clear. 

Zinc has been found in a variety of yellow violet that grows about 
the zinc mines of Aix-la-Chapelle. 

Copper is frequently present in minute quantity in the ash of plants, 
especially of such as grow in the vicinity of manufacturing establish- 
ments, where dilute solutions containing copper are thrown to waste. 

The Salts or Compounds of Metals with Non- 
metals found in the ashes of plants or in the unburned 
plant remain to be considered. 

Of the elements, acids and oxides, that have been 
noticed as constituting the ash of plants, it must be re- 
marked that with the exception of silica, magnesia, oxide 
of iron, and oxide of manganese, they all exist in the 
ash in the form of salts (compounds of acids and bases). 
In the living agricultural plant it is probable that, of 
them all, only silica occurs in the uncombined state. 

We shall notice in the first place the salts which may 
occur in the ash of plants, and shall consider them under 
the following heads, viz. : Carbonates, Sulphates, Phos- 
phates, and Chlorides. As to the Silicates, it is unnec- 
essary to add anything here to what has been already 
mentioned. 



144 HOW CROPS GROW. 

The Carbonates which occur in the ashes of plants 
are those of Potassium, Sodium, and Calcium. The 
Carbonates of Magnesium, Iron, and Manganese are de- 
composed by the heat at which ashes are prepared. 

Potassium Carbonate, or Carbonate of Potash, 
K 2 C0 3 , 114. — The pearl-ash of commerce is a tolerably 
pure form of this salt. When wood is burned, the potash 
which it contains is found in the ash, chiefly as carbon- 
ate. If wood-ashes are repeatedly washed or leached with 
water, all the salts soluble in this liquid are removed ; by 
boiling this solution down to dryness, which is done in 
large iron pots, crude potash is obtained, as a dark or 
brown mass. This, when somewhat purified, yields 
pearl-ash. Potassium carbonate, when pure, is white, and 
has a bitter, biting taste — the so-called alkaline taste. It 
has such attraction for water, that, when exposed to the 
air, it absorbs moisture and becomes a liquid. 

If hydrochloric acid be poured upon this carbonate a 
brisk effervescence immediately takes place, owing to the 
escape of carbon dioxide gas, and potassium chloride and 
water are formed, which remain behind. 

K,C0 3 + 2 HC1 = 2 KC1 -f- H 2 + C0 2 . 

Potassium Bicarbonate, KHC0 3 . — A solution of 
potassium carbonate, when exposed to carbon dioxide, ab- 
sorbs the latter, and the potassium bicarbonate is pro- 
duced, so called because to a given amount of potassium 
it contains twice as much carbonic acid as the carbonate. 
Potash-salceratus consists essentially of this salt. It 
probably exists in the juices of various plants. 

Sodium Carbonate, or Carbonate of Soda, 
Ka 2 CO s , 106. — This substance, so important in the arts, 
was formerly made from the ashes of certain marine 
plants (Salsola and Salicornia), in a manner similar to 
that now employed in wooded countries for the prepara- 
tion of potash. It is at present almost wholly obtained 



THE ASH OF PLANTS. 145 

from common salt by somewhat complicated processes. 
It occurs in commerce in an impure state under the name 
of Soda-ash. United to water, it forms sal-soda, which 
usually exists in transparent crystals or crystallized 
masses. These contain 03 per cent of water, which 
partly escapes when the salt is exposed to the air, leav- 
ing a white, opaque powder. 

Sodium carbonate has a nauseous alkaline taste, not 
nearly so decided, however, as that of the carbonate of 
potassium. It is often present in the ashes of plants. 

Sodium Bicarbonate, NaHC0 8 . — The supercarlon- 
ate of soda of the apothecary is this salt in a nearly pure 
state. The cooking-soda of commerce is a mixture of 
this with some simple carbonate. It is prepared in the 
same way as potassium bicarbonate. The bi carbonates, 
both of potassium and sodium, give off half their carbonic 
acid at a moderate heat, and lose all of this ingredient 
by contact with excess of any acid. Their use in baking 
depends upon these facts. They neutralize any acid 
(lactic or acetic) that is formed during the " rising " of 
the dough, and assist to make the bread " light" by in- 
flating it with carbon dioxide. 

Calcium Carbonate, or Carbonate of Lime, 
CaC0 3 , 112. — This compound is the white powder formed 
by the contact of carbon dioxide with lime-water. When 
slacked lime is exposed to the air, the water it contains 
is gradually displaced by carbon dioxide, aud carbonate of 
lime is the result. Air-slacked lime always contains 
much carbonate. This salt is distinguished from lime 
by its being destitute of any alkaline taste. 

In nature carbonate of lime exists to an immense ex- 
tent as coral, chalk, marble, and limestone. These 
rocks, when strongly heated, especially in a current of 
air, part with carbon dioxide, and quick-lime remains 
behind. 

Calcium carbonate occurs largely in the ashes of most 
10 



146 HOW CKOPS GROW. 

plants, particularly of trees. In the manufacture of 
potash it remains undissolved, and constitutes a chief 
part of the residual leached ashes. 

The calcium carbonate found in the ashes of plants is 
supposed to come mainly from the decomposition by heat 
of organic calcium salts (oxalate, tartrate, malate, etc.), 
which exist in the juices of the vegetable, or are abun- 
dantly deposited in its tissues in the solid form. Car- 
bonate of lime itself is, however, not an unusual compo- 
nent of vegetation, being found in the form of minute, 
rhombic crystals, in the cells of a multitude of plants. 

The Sulphates which we shall notice at length are 
those of Potassium, Sodium, and Calcium. . Sulphate of 
Magnesium is well known as Epsom salts, and Sulphate 
of Iron is copperas or green vitriol. 

Potassium Sulphate, or Sulphate of Potash, 
K 2 S0 4 , 174. — This salt may be procured by dissolving 
potash or carbonate of potash in diluted sulphuric acid. 
On evaporating its solution, it is obtained in the form of 
hard, brilliant crystals, or as a white powder. It has a 
bitter taste. Ordinary potash, or pearl-ash, contains 
several per cent of this salt. 

Sodium Sulphate, or Sulphate of Soda, Na 2 S0 4 , 
142. — Glauber's salt is the common name of this famil- 
iar substance. It has a bitter taste, and is much em- 
ployed as a purgative for cattle and horses. It exists, 
either crystallized and transparent, containing 10 mole- 
cules, or nearly 56 per cent of water, or anhydrous. 
The crystals rapidly lose their water when exposed to the 
air, and yield the anhydrous salt as a white powder. 

Calcium Sulphate, or Sulphate of Lime, CaS0 4 , 
136. — The burned Plaster of Paris of commerce is this 
salt in a more or less pure state. It is readily formed by 
pouring diluted sulphuric acid on lime or marble. It is 
found in the ash of most plants, especially in that of 
clover, the bean, and other legumes. 



THE ASH OF PLANTS. 14? 

Iii nature, sulphate of lime is usually combined with 
two molecules of water, and thus constitutes Gypsum, 
CaS0 4 .2 H 2 0, which is a rock of frequent and exten- 
sive occurrence. In the cells of many plants, as for 
instance the bean, gypsum may be discovered by the 
microscope in the shape of minute crystals. It requires 
400 times its weight of water to dissolve it, and being 
almost universally distributed in the soil, is rarely absent 
from the water of wells and springs. 

Land plaster is ground gyj^sum, that from Nova 
Scotia being white, that from Onondaga and other local- 
ities in New York State gray in color. 

The Phosphates which require special description 
are those of Potassium, Sodium, and Calcium. 

Numerous phosphates of each of these bases exist, or 
may be prepared artificially. But three classes of phos- 
phates have any immediate interest to the agriculturist. 
As has been stated (p 132), phosphoric acid, prepared by 
boiling phosphorus pentoxide with water, is represented 
by the symbol H 3 P0 4 . The phosphates may be regarded 
as phosphoric acid in which one, two, or all the atoms 
of hydrogen are substituted by one or several metals. 

Potassium Phosphates or Phosphates of Potash. 
— There are three of these phosphates formed by replac- 
ing one, two, or three hydrogen atoms of phosphoric 
acid by potassium, viz. : KH 2 P0 4 , primary or mono- 
potassic phosphate ; K 2 HP0 4 , secondary or dipotassic 
phosphate, and K 3 P0 4 , tertiary or tripotassic phos- 
phate.* Of these salts, the secondary and tertiary phos- 
phates exist largely (to the extent of 40 to 50 per cent) 
in the ash of the kernels of wheat, rye, maize, and other 
bread grains. The potassium phosphates do not occur 
in commerce ; they closely- resemble the corresponding 
sodium-salts in their external characters. 



*The primary phosphates are often designated acid or super-phos- 
phates, the secondary neutral jihosphates, and the tertiary basic phos- 
phates. 



148 HOW CROPS GROW. 

Sodium Phosphates, or Phosphates of Soda.— 

Of these the disodic phosphate, Na 2 HP0 4 , alone needs 
notice. It is found in the drug-stores in the form of 
glassy crystals, which contain 12 molecules (56 per cent) 
of water. The crystals become opaque if exposed to the 
air, from the loss of water. This salt has a cooling, sa- 
line taste, and is very soluble in water. 

Calcium Phosphates, or Phosphates of Lime. 
— Since one atom of calcium replaces two of hydrogen, 
the formula? of the calcium phosphates are written as 
follows : monocalcic or primary phosphate CaH 4 P 2 8 ; 
dicalcic or secondary phosphate, CaHP0 4 ; tricalcic or 
tertiary phosphate, Ca 3 P 2 8 .* Both the secondary and 
tertiary phosphates probably occur in plants. The sec- 
ondary is a white crystalline powder, nearly insoluble 
in water, but easily soluble in acids. In nature it is 
found as a urinary concretion in the sturgeon of the Cas- 
pian Sea. It is also an ingredient of guanos, and proba- 
bly of animal excrements in general. 

The tricalcic phosphate, or, as it is sometimes termed, 
lone-phosphate, is a chief ingredient of the bones of ani- 
mals, and constitutes 90 to 95 per cent of the ash or 
earth of bones. It may be formed by adding a solution 
of lime to one of sodium phosphate, and appears as a 
white precipitate. It is insoluble in pure water, but dis- 
solves in acids and in solutions of many salts. In the 
mineral kingdom tricalcic phosphate is the chief ingre- 
dient of apatite and phosphorite. These minerals are 
employed in the preparation of the commercial super- 
phosphates now consumed to an enormous extent as a 
fertilizer. Plain superphosphate is essentially a mixture 
of sulphate of lime with the three phosphates above no- 
ticed and with free phosphoric acid. 

The Phosphates of Magnesium, Iron, Alumin- 
ium and Manganese, are bodies insoluble in water, 



* These formulae correspond to 2 molecules of phosphoric acid, 
=H 6 P 2 8 , with 2 and 4 H-atoms replaced by Ca. 



THE ASH OF PLAXTS. 149 

that occur in very small proportion in the ashes of plants 
and in soils, but are important ingredients of some 
fertilizers. 

The Chlorides are all characterized by their ready 
solubility in water. The Chlorides of Calcium and Mag- 
nesium are deliquescent, i. e., they liquefy by absorbing- 
moisture from the air. The Chlorides of Potassium and 
Sodium alone need to be described. 

Potassium Chloride, or Muriate of Potash, 
K.C1, 74.5. — This body may be produced either by expos- 
ing metallic potassium to chlorine gas, in which case the 
two elements unite together directly ; or by dissolving 
caustic potash in hydrochloric acid. In the latter case 
water is also formed, as is expressed by the equation 
KHO + HC1 = KC1 +'H 2 0. 

Potassium chloride closely resembles common salt in 
appearance, solubility in water, taste, etc. It is now an 
important article of commerce and largely consumed as 
a fertilizer. It is also often present in the ash and in 
the juices of plants, especially of sea-weeds, and is like- 
wise found in most fertile soils. 

Chloride of Sodium, Nad, 58.5. — This substance is 
common or culinary salt. Ifc was formerly termed muri- 
ate of soda. It is scarcely necessary to speak of its oc- 
currence in immense quantities in the water of the ocean, 
in saline springs, and in the solid form as rock-salt, in 
the earth. Its properties are so familiar as to require no 
description. It is rarely absent from the ash of plants. 

Besides the salts and compounds just described, there 
occur in the living plant other substances, most of which 
have been indeed already alluded to, but may be noticed 
again connectedly in this place. 

These compounds, being destructible by heat, do not 
appear in the analysis of the ash of a plant. 

Nitrates. — Nitric acid (the compound by which ni- 
trogen is chiefly furnished to plants for the elaboration 



150 HOW CROPS GROW. 

of the albuminoid principles) is not unfrequently pres- 
ent as a nitrate in the tissues of the plant. It usually 
occurs there as potassium nitrate (niter, saltpeter), 
KN0 3 . 

The properties of this salt scarcely need description. 
It is a white, crystalline body, readily soluble in water, 
and has a cooling, saline taste. When heated with car- 
bonaceous matters, it yields oxygen to them, and a defla- 
gration, or rapid and explosive combustion, results. 
Touch-paper is paper soaked in solution of niter and 
dried. The leaves of the sugar-beet, sunflower, tobacco, 
and some other plants, frequently contain this salt, and, 
when burned, the nitric acid is decomposed, often with 
slight deflagration, or glowing like touch-paper, and the 
alkali remains in the ash as carbonate. The characters 
of nitric acid and the nitrates are noticed at length in 
" How Crops Feed." See also p 

Oxalates, Citrates, Malates, Tartrates, and salts 
of other less common organic acids, are generally to be 
found in the tissues of living plants. On burning, the 
metals with 'which they were in combination — potassium 
and calcium, in most cases — remain as carbonates. 

Ammonium Salts exist in minute amount in some 
plants. What particular salts thus occur is uncertain, 
and special notice of them is unnecessary in this chapter. 

Since it is possible for each of the acids above described 
to unite with each of the bases in one or several propor- 
tions, and since we have as many oxides and chlorides as 
there are metals, and even more, the question at once 
arises — which of the 60 or more compounds that may thus 
be formed outside the plant do actually exist within it ? 
In answer, we must remark that while most or all of them 
may exist in the plant but few have been proved to exist 
as such in the vegetable organism. As to the state in 
which iron and manganese occur, we know little or noth- 
ing, and we cannot always assert positively that in a given 



THE ASH OF PLANTS. 151 

plant potassium exists as phosphate, or sulphate, or car- 
bonate. We judge, indeed, from the predominance of 
potassium and phosphoric acid in the ash of wheat, that 
potassium phosphate is a large constituent of this grain, 
but of this we are scarcely certain, though in the absence 
of evidence to the contrary we are warranted in assuming 
these two ingredients to be united. On the other hand, 
calcium carbonate and calcium sulphate have been discov- 
ered by the microscope in the cells of various plants, in 
crystals whose characters are unmistakable. 

For most purposes it is unnecessary to know more than 
that certain elements are present, without paying atten- 
tion to their mode of combination. And yet there is 
choice in the manner of representing the composition of 
a plant as regards its ash-ingredients. 

We do not indeed so commonly speak of the calcium 
or the silicon in the plant as of lime and silica, because 
these rarely-seen elements are much less familiar than 
their oxides. 

Again, we do not speak of the sulphates or chlorides, 
when we desire to make statements which may be com- 
pared together, because, as has just been remarked, we 
cannot always, nor often, say what sulphates or what 
chlorides are present. 

In the paragraphs that follow, which are devoted to a 
more particular statement of the mode of occurrence, rel- 
ative abundance, special functions, and indispensability 
of the fixed ingredients of plants, will be indicated the 
customary methods of defining them. 

§2. 

QUANTITY, DISTRIBUTION, AND VARIATIONS OF THE ASH- 
INGREDIENTS. 

The Ash of plants consists of the various acids, oxides, 
and salts, that have been noticed in § 1, which are fixed 
or n on- volatile at a heat near redness. 



152 HOW CROPS GROW. 

Ash-ingredients are always present in eachceli of every 
plant. 

The ash-ingredients exist partly in the cell-wall, in- 
crusted or imbedded in the cellulose, and partly in the 
plasma or contents of the cell (see p 249). 

One portion of the ash-ingredients is soluble in water, 
and occurs in the juice or sap. This is true, in general, 
of the salts of the alkali-metals, and of the sulphates and 
chlorides of magnesium and calcium. Another portion 
is insoluble, and exists in the tissues of the plant in the 
solid form. Silica, the calcium phosphates and the mag- 
nesium compounds, are mostly insoluble. 

The ash-ingredients may be separated from the volatile 
matter by burning or by any process of oxidation. In 
burning, portions of sulphur, chlorine, alkalies, and phos- 
phorus may be lost, under certain circumstances, by vola- 
tilization. The ash remains as a skeleton of the plant, 
and often actually retains and exhibits the microscopic 
form of the tissues. 

The Proportion of Ash is not Invariable, even in 
the same kind of plant, and in the same part of the plant. 
Different kinds of plants often manifest very marked dif- 
ferences in the quantity of ash they contain. The fol- 
lowing table exhibits the amount of ash in 1 00 parts (of 
dry matter) of a number of plants and trees, and in their 
several parts. In most cases is given an average proportion 
as deduced from a large number of the most trustworthy 
examinations. In some instances are cited the extreme 
proportions hitherto put on record. 

PROPORTIONS OF ASH IN VARIOUS VEGETABLE MATTERS.* 
ENTIRE PLANTS, ROOTS EXCEPTED. 

Average. Average. 

Red clover 6.7 Turnips, 10.7—19.7 15.5 

White " 7.2 Carrot, 15.0—21.3 17.1 

Timothy 7.1 Hops 9.9 

Potatoes 5.1 Hemp 4.6 

Sugar beet, 16.3—18.6 17.5 Flax 4.3 

Field beet, 14.0—21.8 18.2 Heath 4.5 



* These figures are copied unchanged from the old edition, and may 
differ from later averages, but are approximately correct. 



THE ASH OF PLANTS. 153 



ROOTS A>'D TUBERS. 



Potatoes, 2.6—8.0 4.1 

Sugar beet, 2.9—6.0 4.4 

Field beet, 2.8—11.3 7.7 



Turnip, 6.0—20.9 12.0 

Carrot, 5.1—10.9 8.2 

Artichoke 5.2 



STRAW AND STEMS. 



Wheat, 3.8—6.9 5.4 

Rye, 4.9—5.6 5.3 

Oats, 5.0—5.4 5.3 

Barley 6.8 



Peas, 6.5—9.4 7.9 

Beans, 5.1—7.2 6.1 

Flax 3.7 

Maize 5.5 



GRAINS AND SEED. 

Wheat, 1.5—3.1 2.0 Buckwheat, 1.1—2.1 1.4. 

Rye, 1.6—2.7 2.0 Peas, 2.4—2.9 2.7 

Oats, 2.5—4.0 3.3 Beans, 2.7— 4.3 3.7 

Barley, 1.8— 2.8 2.3 Flax, 3.6 

Maize*, 1.3— 2.1 1.5 , Sorghum 1.9 

WOOD. 

Beech 1.0 | Red Pine 0.3 

Birch 0.3 ! White Pine 0.3 

Grape 2.7 , Fir 0.3 

Apple 1.3 | Larch 0.3 



BARK. 



Birch 1.3 

Red Fine 2.8 

White Pine 3.3 



Fir 2.0 

Walnut 6.4 

Cauto tree ' 34.4 



From the above table we gather : — 

1. That different plants yield different quantities of 
ash. It is abundant in succulent foliage, like that of the 
beet (18 per cent), and small in seeds, wood, aud bark. 

2. That different parts of the same plant yield unlike 
proportions of ash. Thus the wheat kernel contains 2 
per cent, while the straw yields 5.4 per cent. The ash 
in sugar-beet tops is 17.5 ; in the roots, 4.4 per cent. 
In the ripe oat, Arendt found (Das Wachsthum der 
Haferpflanze, p. 84), 

In the three lower joints of the stem. . . 4.6 per cent of ash. 
In the two middle joints of the stem — 5.3 " " 

In the one upper joint of the stem 6.4 " " 

In the three lower leaves 10.1 " " 

In the two upper leaves 10.5 " " 

In the ear 2.6 " " 

3. We further find that, in general, the upper and 
outer parts of the plant contain the most ash-ingredi- 
ents. In the oat, as we see from the above figures of 
Arendt, the ash increases from the lower portions to the 
upper, until we reach the ear. If, however, the ear be 



154 HOW CROPS GROW. 

dissected, we shall find that its outer parts are richest in 
ash. Norton found 

In the husked kernels of brown oats 2.1 per cent of ash. 

In the husk of brown oats 8.2 " " 

In the chaff of brown oats 19.1 " " 

Norton also found that the top of the oat-leaf gave 
16.22 per cent of ash, while the bottom yielded but 13.66 
per cent. (Am. Jour. Science, Vol. Ill, 1847.) 

From the table it is seen that wood (03 to 2.7 per 
cent) and seeds (1.5 to 3.7 per cent) — lower or inner 
parts of the plant — are poorest in ash. The stems of 
herbaceous plants (3.7 to 7.9 per cent) are next richer, 
while the leaves of herbaceous plants, which have such 
an extent of surface, are the richest of all (6 to 8 per 
cent). 

4. Investigation has demonstrated further that the 
same plant in different stages of growth varies in the pro- 
portions of ash in dry matter, yielded both by the entire 
plant and by the several organs or parts. 

The following results, obtained by Norton, on the oat, 
illustrate this variation. Norton examined the various 
parts of the oat-plant at intervals of one week through- 
out its entire period of growth. He found 

Leaves. Stem. Knots. Chaff. Grain unhusked. 

June 4 10.8 10.4 

June 11 10.7 9.8 

June 18 9.0 9.3 

June 25 10.9 9.1 

July 2 11.3 7.8 4.9 

July 9 12.2 7.8 4.3 

July 16 12.6 7.9 6.0 3.3 

July 23 16.4 7.9 10.0 9.1 3.6 

July 30 16.4 7.4 9.6 12.2 4.2 

Aug. 6 16.0 7.6 10.4 13.7 4.3 

Aug. 13 20.4 6.6 10.4 18.6 4.0 

Aug. 20 21.1 6.6 11.7 21.0 3.6 

Aug. 27 22.1 7.7 11.2 22.4 3.5 

Sept. 3 20.9 8.3 10.7 27.4 3.6 

Here, in case of the leaves and chaff, we observe a con- 
stant increase of ash, while in the stem there is a con- 



THE ASH OF PLANTS. 155 

stant decrease, except at the time of ripening, when these 
relations are reversed. The knots of the stem preserved 
a pretty uniform ash-content. The unhusked grain at 
first suffered a diminution, then an increase, and lastly a 
decrease again. 

Arendt found in the oat-plant fluctuations, not in all 
respects accordant with those observed by Norton. 
Arendt obtained the following proportions of ash : 

3 lower 2 middle Upper Lower Upper Entire 

joints of joints of joint of leaves, leaves. Ears, plant, 
stem. stem. stem. 

June 18 4.4 9.7 7.7 8.0 

June 30 2.5 2.9 3.5 9.4 7.0 3.8 5.2 

July 10 3.5 4.7 5.2 10.2 6.9 3.6 5.4 

July 21 4.4 5.0 5.5 10.1 9.7 2.8 5.2 

July 31 6.4 5.3 6.4 10.1 10.5 2.6 5.1 

Here we see that the ash increased in the stem and in 
each of its several parts after the first examination. The 
lower leaves exhibited an increase of fixed matters after 
the first period, while in the upper leaves the ash dimin- 
ished toward the third period, and thereafter increased. 
In the ears, and in the entire plant, the ash decreased 
quite regularly as the plant grew older. Pierre found 
that the proportion of ash of the colza (Brassica olera- 
cea) diminished in all parts of the plant (which was 
examined at five periods), except in the leaves, in which 
it increased. (Jahresberir.ht iiber Agriculturchemie, III, 
p. 122.) The sugar-beet (Bretschneider) and potato 
(Wolff) exhibit a decrease of the per cent of ash, both in 
tops and roots. 

In the turnip, examined at four periods, Anderson 
(Trans. High, and Ag. /Sbc. , 1859-61, p. 371) found the 
following per cent of ash in dry matter : 

July 7. Aug. 11. Sept. 1. Oct. 5. 

Leaves 7.8 20.6 18.8 16.2 

Bulbs 17.7 8.7 10.2 20.9 

In this case, the ash of the leaves increased during 
about half the period of growth from 7.8 to 20.6, and 



156 HOW CROPS GROW. 

thence diminished to 16.2. The ash of the bulbs fluc- 
tuated in the reverse manner, falling from 17.7 to 8.7, 
then rising again to 20. 9. 

In general, the proportion of ash of the entire plant 
diminishes regularly as the plant grows old. 

5. The influence of the soil and season in causing the 
proportion of ash of the game kind of plant to vary, is 
shown in the following results, obtained by Wunder 
Versuchs-Stationen, IV, p. 266) on turnip bulbs, raised 
during two successive years, in different soils. 

In sandy soil. In loamy soil. 

, * v , * s 

1st year. 2d year. 1st year. 2d year. 
Per cent of ash 13.9 11.3 9.1 10.9 

6. As might be anticipated, different varieties of the 
same plant, grown on the same soil, take up different 
quantities of n on- volatile matters. 

In five varieties of potatoes, cultivated in the same soil 
and under the same conditions, Herapath (Qu. Jour. 
C'hem., Soc. II, p. 20) found the percentages of ash in 
dry matter of the tuber as follows : 

VARIETY OF POTATO. 

White Prince's Axbridge Forty- 

Apple. Beauty. Kidney. Magpie, fold. 
Ash per cent... 4.8 3.6 4.3 3.4 3.9 

7. It has been observed further that different individ- 
uals of the same variety of plant, growing side by side, 
on the same soil (in the same field, at least), contain dif- 
ferent proportions of ash-ingredients, according as they 
are, on the one hand, healthy, vigorous plants, or, on the 
other, ivealc and stunted. Pierre (Jahresbericht itber 
Agriculturchemie, III, p. 125) found in entire colza 
plants of various degrees of vigor the following percent- 
ages of ash in dry matter : 

In extremely feeble plants, 1856 8.0 per cent of ash. 

In very feeble plants, 1857 9.0 " " 

In feeble plants, 1857 11.4 " " 

In strong plants, 1857 11.0 " " 

In extremely strong plants, 1857 14.3 " " 



THE ASH OF PLANTS. 157 

Pierre attributes the larger per cent of ash in the 
strong plants to the relatively greater quantity of leaves 
developed on them. 

Similar results were obtained by Arendt in case of oats. 
Wunder ( Versuchs-St.. IV, p. 115) found that the leaves 
of small turnip-plants yielded somewhat more ash per 
cent than large plants. The former gave 19.7, the lat- 
ter 16.8 per cent. 

8. The reader is prepared from several of the foregoing 
statements to understand partially the cause of the vari- 
ations in the proportion of ash in different specimens of 
the same kind of plant. 

The fact that different parts of the plant are unlike in 
their composition, the upper and outer portions being, in 
general, the richer in ash-ingreclients, may explain in 
some degree why different observers have obtained differ- 
ent analytical results. 

It is well known that very many circumstances influ- 
ence the relative development of the organs of a plant. 
In a dry season, plants remain stunted, are rougher on 
the surface, having more and harsher hairs and prickles, 
if these belong to them at all, and develop fruit earlier 
than otherwise. In moist weather, and under the influ- 
ence of rich manures, plants are more succulent, and the 
stems and foliage, or vegetative parts, grow at the ex- 
pense of the reproductive organs. Again, different vari- 
eties of the same plant, which are often quite unlike in 
their style of development, are of necessity classed to- 
gether in our table, and under the same head are also 
brought together plants gathered at different stages of 
growth. 

In order that the wheat plant, for example, should 
always have the same percentage of ash, it would be nec- 
essary that it should always attain the same relative de- 
velopment in each individual part. It must, then, 
always grow under the same conditions of temperature, 



158 HOW CROPS GROW. 

light, moisture, and soil. This is, however, as good as 
impossible, and if we admit the wheat plant to vary in 
form within certain limits without losing its proper char- 
acteristics, we must admit corresponding variations in 
composition. 

The difference between the Tuscan wheat, which is 
cultivated exclusively for its straw, of which the Leghorn 
hats are made, and the "pedigree wheat" of Mr. Hallett 
(Journal Roy. Ag. Soc. Eng., Vol. 22, p. 374), is in 
some respects as great as between two entirely different 
plants. The hat wheat has a short, loose, bearded ear, 
containing not more than a dozen small kernels, while 
the pedigree wheat has shown beardless ears of 8f inches 
in length, closely packed with large kernels to the num- 
ber of 120 ! 

Now, the hat wheat, if cultivated and propagated in 
the same careful manner as has been done with the pedi- 
gree wheat, would, no doubt, in time become as prolific 
of grain as the latter, while the pedigree wheat might 
perhaps with greater ease be made more valuable for its 
straw than its grain. 

We easily see then, that, as circumstances are perpet- 
ually making new varieties, so analysis continually finds 
diversities of composition. 

9. Of all the parts of plants, the seeds are the least Ha- 
lle to vary in composition. Two varieties or two indi- 
viduals may differ enormously in their relative propor- 
tions of foliage, stem, chaff, and seed ; but the seeds 
themselves nearly agree. Thus, in the analysis of 67 
specimens of the wheat kernel, collated by the author, 
the extreme percentages of ash were 1.35 and 3.13. In 
60 specimens out of the 67, the range of variation fell 
between 1.4 and 2.3 per cent. In 42 the range was from 
1.7 to 2.1 per cent, while the average of the whole was 
2.1 per cent. 

In the stems or straw of the grains, the variation is 



THE ASH OF PLANTS. 159 

much more considerable. Wheat-straw ranges from 3.8 
to 6.9 ; pea-straw, from 6.5 to 9.4 per cent. In fleshy 
roots, the variations are great ; thus turnips range from 
6 to 21 per cent. The extremest variations in ash-con- 
tent are, however, found, in general, in the succulent 
foliage. Turnip tops range from 10.7 to 19.7; potato 
tops vary from 11 to near 20, and tobacco from 19 to 27 
per cent. 

Wolff {Die Naturgesetzlichen Grundlagen des Acker- 
baus, 3 Aufl., p. 117) has deduced from a large number 
of analyses the following averages for three important 
classes of agricultural plants, viz. : 

Grain. Straw. 

Cereal c^fcs 2 per cent. 5.25 percent. 

Leguminous crops 3 " " 5 " " 

Oil-plants 4 " " 4.5 " " 

More general averages are as follows (Wolff, he. cit.) : 



Annual and biennial plants. 

Seeds 3 per cent. 

Stems 5 " ". 

Roots 4 " " 

Leaves 15 " " 



Perennial plants. 

Seeds 3 per cent. 

Wood l " " 

Bark 7 " " 

Leaves 10 " " 



We may conclude this section by stating three propo- 
sitions which are proved in part by the facts that have 
been already presented, and which are a summing up of 
the most important points in our knowledge of this sub- 
ject. 

1. Ash-ingredients are indispensable to the life and 
growth of all plants. In mold, yeast, and other plants 
of the simplest kind, as well as in those of the higher or- 
ders, analysis never fails to recognize a proportion of 
fixed matters. We must hence conclude that these are 

■ 

necessary to the primary acts of vegetation, that atmos- 
pheric food cannot be assimilated, that vegetable matter 
cannot be organized, except with the cooperation of those 
substances which are invariably found in the ashes of the 
plant. This proposition is demonstrated in the most 
conclusive manner by numerous synthetic experiments. 



160 HOW CROPS GROW. 

It is, of course, impossible to attempt producing a plant 
at all without some ash -ingredients, for the latter are 
present in all seeds, and during germination are trans- 
ferred to the seedling. By causing seeds to sprout in a 
totally insoluble medium, we can observe what happens 
when the limited supply of fixed matters in the seeds them- 
selves is exhausted. Wiegmann & Polstorf (Preisschrift 
iiber die unorganisclien Bestandtheile der Pflanzen) plant- 
ed 30 seeds of cress in fine platinum wire contained in a 
platinum vessel. The contents of the vessel were moist- 
ened with distilled water, and the whole was placed under 
a glass shade, which served to shield from dust. Through 
an aperture in the shade, connection was made with a gas- 
ometer, by which the atmosphere in the interior could be 
renewed with an artificial mixture, consisting, in 100, of 
21 parts oxygen, 78 parts nitrogen, and 1 part carbonic 
acid. In two days 28 of the seeds germinated ; afterwards 
they developed leaves, and grew slowly with a healthy ap- 
pearance during 26 days, reaching a height of two or 
three inches. From this time on, they refused to grow, 
began to turn yellow, and died down. The plants were 
collected and burned ; the ash from them weighed pre- 
cisely as much as that obtained by burning 28 seeds like 
those originally sown. This experiment demonstrates 
most conclusively that a plant cannot grow in the absence 
of those substances found in its ash. The development 
of the cresses ceased so soon as the fixed matters of the 
seed had served their utmost in assisting the organization 
of new cells. We know from other experiments that, had 
the ashes of cress been applied to the plants in the above 
experiment, just as they exhibited signs of unhealthiness, 
they would have recovered, and developed to a much great- 
er extent. 

II. The proportion of ash-ingredients in the plant is 
variable within a narrow range, but cannot fall below or 
exceed certain limits. The evidence of this proposition 



THE ASH OF PLANTS. 161 

is to be gathered both from the table of ash-percentages 
and from experiments like that of Wiegmann & Polstorf, 
above described. 

III. We have reason to believe that each part or organ 
(each cell) of the plant contains a certain, nearly invaria- 
ble, amount of fixed matters, which is indispensable to the 
vegetative functions. Each part or organ may contain, 
besides, a variable and unessential or accidental quantity 
of the same. What portion of the ash of any plant is es- 
sential and what accidental is a question not yet brought 
to a satisfactory decision. By assuming the truth of this 
proposition, we account for those variations in the 
amount of ash which cannot be attributed to the causes 
already noticed. The evidences of this statement must 
be reserved for the subsequent section. 

5 3. 

SPECIAL COMPOSITION OF THE ASH OF AGRICULTURAL 

PLANTS. 

The result of the extended inquiries which have been 
made into the subject of this section may be convenient- 
ly presented and discussed under a series of propositions, 
viz. : 

1. Among the substances which have been described 
(§ I) as the ingredients of the ash, the following are in- 
variably present in all agricultural plants, and in nearly 
all parts of them, viz. : 

fPotash, K 2 0. rChlorine, CI, 

Soda, Na 2 0. Sulphuric acid, SO,. 

Bases <J Lime, CaO. Acids 1 Phosphoric acid, P,0 5 . 
I Magnesia, MgO. Silicic acid, SiO,. " * 

LOxide of iron, Fe 2 3 . ^Carbonic acid, C0 2 . 

2. Different normal specimens of the same kind of 
plant have a nearly constant composition. The use of 
the word nearly in the above statement implies what has 
been already intimated, viz., that some variation is noticed 
in the relative proportions as well as in the total quantity 

11 



162 HOW CROPS GROW. 

of ash-ingredients occurring in plants. This point will 
shortly be discussed in full. By taking the average of 
many trustworthy ash-analyses we arrive at a result which 
does not differ very widely from the majority of the in- 
dividual analyses. This is especially true of the seeds of 
plants, which attain nearly the same development under 
all ordinary circumstances. It is less true of foliage and 
roots, whose dimensions and character vary to a great 
extent. In the following tables (p. 164-170) is stated the 
composition of the ashes of a number of agricultural 
products which have been repeatedly subjected to analy- 
sis. In most cases, instead of quoting all the individual 
analyses, a series of averages is given. Of these, the first 
is the mean of all the analyses on record or obtainable by 
the writer,* while the subsequent ones represent either 
the results obtained in the examination of a number of 
samples by one analyst, or are the means of several single 
analyses. In this way, it is believed, the real variations 
of composition are pretty truly exhibited, independently 
of the errors of analysis. 

The lowest and highest percentages are likewise given. 
These are doubtless in many cases exaggerated by errors of 
analysis, or by impurity of the material analyzed. Chlo- 
rine and sulphuric acid are for the most part too low, be- 
cause they are liable to be dissipated in combustion, while 
silica is often too high, from the fact of sand and soil ad- 
hering to the plant. 

In two cases, single and doubtless incorrect analyses by 
Bichon, which give exceptionally large quantities of soda, 
are cited separately. 

A number of analyses that came to notice after making 
out the averages are given as additional. 

* At the time of preparing the first edition of this book, in 1868. More 
recent analyses are comparatively few in number, excepting those of 
wheat (grain and straw) bv Lawes & Gilbert, and do not differ essen- 
tially from those given. The numerous very incorrect ash-analyses, 
published by Dr. E. Emmons and Dr. J. H. Salisbury, in the Natural 
History of New York, and in the Trans, of the New York State Agricul- 
tural Society, are not included. 



THE ASH OF PLANTS. 163 

The following table includes both the kernel and straw 
of Wheat, Rye, Barley, Oats, Maize, Eice, Buckwheat, 
Beans, and Peas ; the tubers of Potatoes ; the roots and 
tops of Sugar-Beets, Field-Beets, Carrots, Turnips, and 
various parts of the Cotton Plant. 

For the average composition of other plants and vege- 
table products, the reader is refer red to a table in the ap- 
pendix, p. 409, compiled by Prof. Wolff:, of the Eoyal 
Agricultural Academy of Wiirtemberg. That table in- 
cludes also the averages obtained by Prof. Wolff for most 
of the substances, cotton excepted, w T hose composition is 
represented in the pages immediately following. 

In both tables the carbonic acid, CO 2 , which occurs in 
most ashes, is excluded, from the fact that its quantity 
varies according to the temperature at which the ash is 
prepared. 

The following is a statement of the various Names and 
Symbols that are or have been currently applied to the 
Ash-Ingredients in Chemical Literature. The changes 
that -have been made from time to time, both in symbols 
and in names, are the res alts of progress in knowledge or 
of attempts to improve nomenclature : 

01 'fr Newer 

Synbols. Symbols. Synonyms. 

K0 K 2 Potash, Potassa, Potassium Oxide, Potassic Oxide. 

N&O Na,0 Soda, Sodium Oxide, Sodic Oxide. 

MgO MgO Magnesia, Magnesium Oxide, Magnesic Oxide. 

CaO CaO Lime, Calcium Oxide, Calcic Oxide. 

Fe 2 3 Pe 2 3 Iron Oxide, Peroxide of Iron, Sesquioxide of Iron, 

Ferric Oxide. 

P0 5 P 2 5 Phosphoric Acid, Anhydrous Phosphoric Acid, 

Phosphoric Anhydide, Phosphorus Pentox- 
ide, Phosphoric Oxide. 

S0 3 S0 3 Sulphuric Acid, Anhydrous Sulphuric Acid, Sul- 

phuric Anhydride, Sulphur Trioxide, Sul- 
phuric Oxide. 

Si0 3 Si0 2 Silicic Acid, Anhydrous Silicic Acid, Silicic An- 

hydride, Silicon Dioxide, Silicic Oxide, Silica 
Silex. 

C0 2 C0 2 Carbonic Acid, Anhydrous Carbonic Acid, Car- 

bonic Anhydride, Carbon Dioxide, Carbonic 
Dioxide. 



164 



HOW CROPS GROW. 



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THE ASH OF PLANTS. 171 

The composition of the ash of a number of ordinary 
cropsis concisely exhibited in the subjoined general state- 
ment. 

Amalies. Sa. *»*• P ^ST «««■ WBT «***«. 

Cereals— 

Grain*.... 30 12 3 46 2 2.5 1 

Straw... 13— 27 3 7 5 50—70 2.5 2 

Legumes— 

Kernel... 44 7 5 35 14 2 

Straw... 27—41 7 25—39 8 5 2—6 6—7 

Root Crops— 

Roots.... 60 3—9 6—12 8—18 1—4 5—12 3—9 

Tops.... 37 3—16 10—35 3—8 3 6—13 5—17 

GRASSES— 

In flower.. 33 4 8 8 35 4 5 

3. Different parts of any plant usually exhibit decided 
differences in the composition of their ash. This fact is 
made evident by a comparison of the figures of the table 
above, and is more fully illustrated by the following anal- 
yses of the parts of the mature oat-plant, by Arendt, 1 to 
6 (Die Haferpflanze, p. 107), and Norton, 7 to 9 (Am. 
Jour. Sri,, 2 Ser. 3, 318). 

1 2 34 56789 

Loicer Middle Upper Lower Upper Ears. Chaff. Husk. Kernel 
Stem. Stem. Stem. Leaves. Leaves. husked. 

Potash 81.2 68.3 55.9 36.9 24.8 13.0) 

Soda 0.4 1.5 1.0 0.9 0.4 0.1 J 1°- 06 12A 31-7 

Magnesia 2.1 3.6 3.9 3.8 3.9 8.9) 2.3 8.6 

Lime 3.6 5.3 8.6 16.7 17.2 7.3 I ... 4.3 5.3 

Oxide of Iron.... 1.0 0.0 0.2 2.7 0.5 trace f "** 0.3 0.8 
Phosphoric acid. 2.7 1.4 2.7 1.7 1.5 36.5 J 0.6 49.1 

Sulphuric acid.. 0.0 1.3 1.1 3.2 7.5 4.9 5.3 4.3 0.0 

Silica 4.1 9.3 20.4 34.0 41.8 26.0 68.0 74.1 1.8 

Chlorine 8.6 11.7 7.4 1.6 2.4 3.8 3.1 1.4 0.2 

The results of Arendt and Norton are not in all respects strictly com- 
parable, having been obtained by different methods, but serve well to 
establish the fact in question. 

We see from the above figures that the ash of the lower 
stem consists chiefly of potash (81%). This alkali is pre- 
dominant throughout the stem, but in the upper parts, 
where the stem is not covered by the leaf sheaths, silica 
and lime occur in large quantity. In the ash of the leaves, 
silica, potash, and lime are the principal ingredients. In 
the chaff and husk, silica constitutes three-fourths of the 
ash, while in the grain, phosphoric acid appears as the char- 

♦Exclusive of husk. 



172 HOW CROPS GROW. 

acteristic ingredient, existing there in connection with a 
large amount of potash (32%) and considerable magne- 
sia. Chlorine acquires its maximum (11.7%) in the mid- 
dle stem, but in the kernel is present in small quantity, 
while sulphuric acid is totally wanting in the lower stem, 
and most abundant in the upper leaves. 

Again, the unequal distribution of the ingredients of 
the ash is exhibited in the leaves of the sugar-beet, which 
have been investigated by Bretschneider ( Hoff. Jahresbe- 
riclit, 4, 89). This experimenter divided the leaves of 6 
sugar-beets into 5 series or circles, proceeding from the 
outer and older leaves inward. He examined each series 
separately with the following results: 

I. II. III. IV. v. 

Potash 18.7 25.9 32.8 37.4 50.3 

Soda 15.2 14.4 15.8 15.0 11.1 

Chloride of Sodium.... 5.8 6.4 5.8 6.0 6.5 

Lime 24.2 19.2 18.2 15.8 4.7 

Magnesia 24.5 22.3 13.0 8.9 6.7 

Oxide of Iron 1.4 0.5 0.6 0.6 0.5 

Phosphoric acid 3.3 4.8 5.8 8.4 12.7 

Sulphuric acid 5.4 5.6 5.6 5.2 5.9 

Silica 1.5 0.8 2.7 2.1 1.5 

From these data we perceive that in the ash of the leaves 
of the sugar-beet, potash and phosphoric acid regularly 
and rapidly increase in relation to the other ingredients 
from without inward, while lime and magnesia as rapidly 
diminish in the same direction. The per cent of the other 
ingredients, viz., soda, chlorine, oxide of iron, sulphuric 
acid, and silica, remains nearly invariable throughout. 

Another illustration is furnished by the following anal- 
yes of the ashes of the various parts of the horse-chestnut 
tree made by Wolff {Ackerlau, 2. Auf., 134): 

Ba>k. Wood. Leaf stems. Leaves. Flower-stems. Calyx. 

Potash 12.1 25.7 46.2 27.9 63.6 61.7 

Lime 76.8 42.9 21.7 29.3 9.3 12.3 

Magnesia 1.7 5.0 3.0 2.6 1.3 5.9 

Sulphuric acid trace trace 3.8 9.1 3.5 trace 

Phosphoric acid 6.0 19.2 14.8 22.4 17.1 16.6' 

Silica 1.1 2.6 1.0 4.9 0.7 1.7 

Chlorine 2.8 6.1 12.2 5.1 4.7 2.4 



THE ASH OF PLANTS. 173 

Ripe Fruit. 



Stamens. Petals. Green Fruit. Kernel. Green Brown 

Shell. Shell. 

Fotash 60.7 61.2 58.7 61.7. 75.9 54.6 

Lime 13.8 13.6 9.8 11.5 8.6 16.4 

Magnesia 3.1 3.8 2.4 0.6 1.1 2.4 

Sulphuric acid — trace trace 3.7 1.7 1.0 3.6 

Phosphoric acid... 19.5 17.0 20.8 22.8 5.3 18.6 

Silica 0.7 1.5 0.9 0.2 0.6 0.8 

Chlorine 2.8 38 4.8 2.0 7.6 5.2 , 

4. Similar kinds of plants, and especially the same parts 
of similar plants, exhibit a close general agreement in the 
composition of their ashes ; while plants which are un- 
like in their botanical characters are also unlike in the 
proportions of their fixed ingredients. 

The three plants, wheat, rye, and maize, belong, botan- 
ically speaking, to the same natural order, graminece, and 
the ripe kernels yield ashes almost identical in composi- 
tion. Barley and the oat are also graminaceous plants, 
and their seeds should give ashes of similar composition. 
That such is not the case is chiefly due to the fact, that, 
unlike the wheat, rye, and maize-kernel, the grains of 
barley and oats are closely invested with a husk, which 
forms a part of the kernel as ordinarily seen. This husk 
yields an ash which is rich in silica, and we can only prop- 
erly compare barley and oats with wheat and rye, when 
the former are hulled, or the ash of the hulls is taken out 
of the account. There are varieties of both oats and bar- 
ley, whose husks separate from the kernel — the so-called 
naked or skinless oats and naked or skinless barley — and 
the ashes of these grains agree quite nearly in composi- 
tion with those of wheat, rye, and maize, as may be seen 
from the table on page 174. 

By reference to the table (p. 166), it will be observed 
that the pea and bean kernel, together with the allied 
vetch and lentil (p. 171), also nearly agree in ash-com- 
position. 

So, too, the ashes of the root-crops, turnips, carrots, 



174 HOW CROPS GKOW. 

and beets, exhibit a general similarity of composition, as 
may be seen in the table (p. 168-9). 

Wheat. Rye. Maize. Skinless Skinles 

Averaje Average Average oats. barleys. 

of of rf Analysis Analysis 

seventy-nine twenty-one seven by Fr. by Fr. 

Analyses. Analyses. Analyses. Sc/-ulze. Schulze. 

Potash 31.3 28.8 27.7 33.4 35.9 

Soda 3.2 4.3 4.0 1.0 

Magnesia 12.3 11.6 15.0 11.8 13.7 

Lime 3.2 3.9 1.9 3.6 2.9 

Oxide of Iron 0.7 0.8 1.0 0.8 0.7 

Phosphoric acid 46.1 45.6 47.1 46.9 45.0 

Sulphuric acid 1.2 1 .9 1.7 

Silica 1.9 2.6 2.1 2.4 0.7 

Chlorine 0.2 0.7 0.1 

The seeds of the oil-bearing plants likewise constitute 
a group whose members agree in this respect (p. 170). 

5. The ash of the same species of plant is more or less 
variable in composition, according to circumstances. 

The conditions that have already been noticed as in- 
fluencing the proportion of ash are in general the same 
that affect its quality. Of these we may specially notice : 

a. The stage of growth of the plant. 

b. The vigor of its development. 

c. The variety of the plant or the relative development 
of its parts, and 

d. The soil or the supplies of food. 

a. The stage of growth. The facts that the different 
parts of a plant yield ashes of different composition, and 
that the different stages of growth are marked by the 
development of new organs or the unequal expansion of 
those already formed, are sufficient to sustain the point 
now in question, and render it needless to cite analytical 
evidence. In a subsequent chapter, wherein we shall at- 
tempt to trace some of the various steps in the progress- 
ive development of the plant, numerous illustrations will 
be adduced (p. 241). 

b. Vigor of development. Arendt (Die Haferpflanze, 
p. 18) selected from an oat-field a number of plants in 
blossom, and divided them into three parcels : 1, com- 



THE ASH OF PLANTS. 175 

posed of very vigorous plants ; 2, of medium ; and, 3, of 
very weak plants. He analyzed the ashes of each parcel, 
with results as below : 

1 2 3 

Silica 27.0 39.9 42.0 

Sulphuric acid 4.8 4.1 5.6 

Phosphoric acid 8.2 8.5 8.8 

Chlorine 6.7 5.8 4.7 

Oxide of Iron 0.4 0.5 1.0 

Lime 6.1 5.4 5.1 

Magnesia, Potash and Soda. 45.3 34.3 30.4 

Here we notice that the ash of the weak plants con- 
tains 15 per cent less of alkalies, and 15 per cent more of 
silica, than that of the vigorous ones, while the propor- 
tion of the other ingredients is not greatly different. 

Zoeller (Liebicfs Ernahrung der VegetaUUen, p. 340) 
examined the ash of two specimens of clover which grew 
on the same soil and under similar circumstances, save 
that one, from being shaded by a tree, was less fully de- 
veloped than the other. 

Six weeks after the sowing of the seed, the clover was 
cut, and gave the following results on partial analysis : 

Shaded clover. Unshaded clover. 

Alkalies 54.9 36.2 

Lime 14.2 22.8 

Silica 5.5 12.4 

c. The variety of the plant or the relative development 
of its parts must obviously influence the composition of 
the ash taken as a whole, since the parts themselves are 
unlike in composition. 

Herapath (Qu, Jour. Chem. Soc, II, p. 20) analyzed 
the ashes of the tubers of five varieties of potatoes, raised 
on the same soil and under precisely similar circum- 
stances. His results are as follows : m 

White Prince's A.xbridge 

Apple. Beauty. Kidney. Magpie. Forty-fold. 

Potash 69.7 65.2 70.6 70.0 62.1 

Chloride of Sodium.. 2 - 5 

Lime 3.0 1.8 5.0 5.0 3.3 

Magnesia 6.5 5.5 5.0 2.1 3.5 

Phosphoric acid 17.2 20.8 14.9 14.4 20.7 

Sulphuric acid 3.6 6.0 4.3 7.5 7.9 

Silica °- 2 



176 HOW CROPS GROW. 

d. The soil, or the supplies of food, manures included, 
have the greatest influence in varying the proportions of 
the ash-ingredients of the plant. It is to a considerable 
degree the character of the soil which determines the 
vigor of the plant and the relative development of its 
parts. This condition, then, to a certain extent, in- 
cludes those already noticed. 

It is well known that oats have a great range of weight 
per bushel, being nearly twice as heavy, when grown on 
rich land, as when gathered from a sandy, inferior soil. 
According to the agricultural statistics of Scotland, for 
the year 1857 (Trans. Highland and Ag. Soc, 1857-9, 
p. 213), the bushel of oats produced in some districts 
weighed 44 pounds per bushel, while in other districts it 
was as low as. 35 pounds, and in one instance but 24 
pounds per bushel. Light oats have a thick and bulky 
husk, and an ash-analysis gives a result quite unlike that 
of good oats. Herapath (Jour. Roy. Ag. Society, XI, 
p. 107) has published analyses of light oats from sandy 
soil, the yield being six bushels per acre, and of heavy 
oats from the same soil, after " warping,"* where the 
produce was 64 bushels per acre. Some of his results, 
per cent, are as follows : 

Light oats. Heavy oats. 

Potash 9.8 13.1 

Soda 4.6 7.2 

Lime 6.8 4.2 

Phosphoric acid 9.7 17.6 

Silica 56.5 45.6 

Wolff (Jour, far Prakt. Chem., 52, p, 103) has anal- 
ysed the ashes of several plants, cultivated in a poor soil, 
with the addition of various mineral fertilizers. The in- 
fluence of the added substances on the composition of the 
plant is very striking. The following figures comprise 
his results on the ash of buckwheat straw, which grew 

* Thickly covering with sediment from muddy tide-water. 



THE ASH OF PLANTS. 177 

on the immanured soil, and on the same, after applica- 
tion of the substances specified below : 

12 3 4 5 6 

Unma- Chloride Nitrate Carbonate Su 7 phate Carbonate 
nured. of of of of of 

sodium, potash, potash, magnesia. lime. 

Potash 31.7 21.6 39.6 40.5 28.2 23.9 

Chloride of potassium.... 7.4 26.9 0.8 3.1 6.9 9.7 

Chloride of sodium 4.6 3.0 3.2 3.8 3.4 1.7 

Lime 15.7 14.0 12.8 11.6 14.1 18.6 

Magnesia 1.7 1.9 3.3 1.4 4.7 4.2 

Sulphuric acid. ..» 4.7 2.8 2.7 4.3 7.1 3.5 

Phosphoric acid 10.3 9.5 6.5 8.9 10.9 10.0 

Carbonic acid 20.4 16.1 27.1 22.2 20.0 23.2 

Silica 3.6 4.2 4.2 4.2 4.8 5.2 

100.0 100.0 100.0 100.0 100.0 100.0 

It is seen from these figures that all the applications 
employed in this experiment exerted a manifest influ- 
ence, and, in general, the substance added, or at least one 
of its ingredients, is found in the plant in increased 
quantity. 

In 2, chlorine, but not sodium ; in 3 and 4, potash ; 
in 5, sulphuric acid and magnesia, and in 6, lime, are 
present in larger proportion than in the ash from the 
unmanured soil. 

6. What is the normal composition of the ash of a 
plant ? It is evident from the foregoing facts and con- 
siderations that to pronounce upon the normal composi- 
tion of the ash of a plant, or, in other words, to ascer- 
tain what ash-ingredients and what proportions of them 
are proper to any species of plant or to any of its parts, 
is a matter of much difficulty and uncertainty. 

The best that can be done is to adopt the average of a 
great number of trustworthy analyses as the approximate 
expression of ash-composition. From such data, how- 
ever, we are still unable to decide what are the abso- 
lutely essential, and what are really accidental, ingredi- 
ents, or what amount of any given ingredient is essential, 
and to what extent it is accidental. Wolff, who appears 
to have first suggested that a part of the ash of plants 
12 



178 HOW CROPS GROW. 

may be accidental, endeavored to approach a solution of 
this question by comparing together the ashes of sam- 
ples of the same plant, cultivated under the same circum- 
stances in all respects, save that they were supplied with 
unequal quantities of readily-available ash-ingredients. 
The analyses of the ashes of buckwheat-stems, just 
quoted, belong to this investigation. Wolif showed that, 
by assuming the presence in each specimen of buckwheat- 
straw of a certain excess of certain ingredients, and de- 
ducting the same from the total ash, the residuary ingre- 
dients closely approximated in their proportions to those 
observed in the crop which grew in an unmanured soil. 
The analyses just quoted (p. 163) are here "corrected" 
in this manner, by the subtraction of a certain per cent 
of those ingredients which in each case were furnished 
to the plant by the fertilizer applied to it. The num- 
bers of the analyses correspond with those on the previ- 
ous page. 

12 3 4 5 6 

20 p. c. 20 p. c. 25 p. c. 85 p. c. 16.6 p. c. 
Chloride Carbonate Carbonate Sulphate Carbonates 
After deduction of of of of ofcalc'mani 

of. Nothing, potas- potas- potas- magne- magne- 
sium, sium. sium. stum. sium. 

Potash 31.7 27.0 32.5 33.5 30.6 28.0 

Chloride of potassium. 7.4 9.1 1.0 3.9 7.4 11.3 

Chloride of sodium ... 4.6 3.8 4.0 4.7 3.7 1.9 

Lime 15.7 17.3 16.0 14.5 15.3 14.6 

Magnesia 1.7 2.4 4.1 1.7 2.3 2.9 

Sulphuric acid 4.7 3.5 3.4 5.4 2.1 4.1 

Phosphoric acid 10.3 11.7 8.1 11.2 11.8 11.7 

Carbonic acid 20.4 20.1 25.9 19.8 21.6 19.3. 

Silica 3.6 5.2 5.2 5.3 5.2 6.1 

100.0 100.0 100.0 100.0 100.0 100.0 

The correspondence in the above analyses thus " cor- 
rected," already tolerably close, might, as "Wolff remarks 
(loc. cit.), be made much more exact by a further correc- 
tion, in which the quantities of the two most variable in- 
gredients, viz., chlorine and sulphuric acid, should be 
reduced to uniformity, and the analyses then be recalcu- 
lated to per cent. 



THE ASH OF PLANTS. 179 

In the first place, however, we are not warranted 
in assuming that the " excess " of potassium chloride, 
potassium carbonate, etc., deducted in the above analyses 
respectively, was' all accidental and unnecessary to the 
plant, for, under the influence of an increased amount of 
a nutritive ingredient, the plant may not only mechani- 
cally contain more, but may chemically employ more in 
the vegetative processes. It is well proved that vegeta- 
tion, grown under the influence of large supplies of nitro- 
genous manures, contains an increased proportion of 
truly assimilated nitrogen as albuminoids, amido-acids, 
etc. The same may be equally true of the various ash- 
ingredients. 

Again, in the second place, we cannot say that in any 
instance the minimum quantity of any ingredient neces- 
sary to the vegetative acts is present, and no more. 

It must be remarked that these great variations are 
only seen when we compare together plants produced on 
poor soils, i. e., on those which are relatively deficient in 
some one or several ingredients. If a fertile soil had 
been employed to support the buckwheat plants in these 
trials, we should doubtless have had a very different 
result. 

In 1859, Metzdorf (Wilda's Centralblatt, 1862, II, p. 
367) analysed the ashes of eight samples of the red- 
onion potato, grown on the same field in Silesia, but dif- 
ferently manured. 

Without copying the analyses, we may state some of 
the most striking results. The extreme range of varia- 
tion in potash was 5J per cent. The ash containing the 
highest percentage of potash was not, however, obtained 
from potatoes that had been manured with 50 pounds of 
this substance, but from a parcel to which had been ap- 
plied a poudrette containing less than three pounds of 
potash for the quantity used. 

The unmanured potatoes were relatively the richest in 



180 HOW CHOPS GROW. 

lime, phosphoric acid, and sulphuric acid, although sev- 
eral parcels were copiously treated with manures contain- 
ing considerable quantities of these substances. These 
facts are of great interest in reference to the theory of 
the action of manures. 

7. To what extent is each ash-ingredient essential, 
and how far may it be accidental ? Before chemical 
analysis had arrived at much perfection, it was believed 
that the ashes of the plant were either unessential to 
growth, or else were the products of growth — were gener- 
ated by the plant. 

Since the substances found in ashes are universally dis- 
tributed over the earth's surface, and are invariably pres- 
ent in all soils, it is not possible, by analysis of the ash 
of plants growing under natural conditions, to decide 
whether any or several of their ingredients are indispen- 
sable to vegetative life. For this purpose it is necessary 
to institute experimental inquiries, and these have been 
prosecuted with great painstaking, and with highly val- 
uable results. 

Experiments in Artificial Soils. — The Prince Salm- 
Horstmar, of Germany, was one of the first and most 
laborious students of this question. His plan of experi- 
ment was the following : The seeds of a plant were sown 
in a soil-like medium (sugar-charcoal, pulverized quartz, 
purified sand) which was as thoroughly as possible freed 
from the substance whose special influence on growth 
was the subject of study. All other substances presum- 
ably necessary, and all the usual external conditions of 
growth (light, warmth, moisture, etc.), w r ere supplied. 

The results of 195 trials thus made with oats, wheat, 
barley, and colza, subjected to the influence of a great 
variety of artificial mixtures, have been described, the 
most important of which will shortly be given. 

Experiments in Solutions. — Water-Culture. — 
Sachs, W. Knop, Stohmann, Nobbe, Siegert, and others 



THE ASH OF PLANTS. 



181 



have likewise studied this subject. Their method was 
like that of Prince Salm-Horstmar, except that the plants 
were made to germinate and grow independently of any 
soil; and, throughout the experiment, had their roots im- 
mersed in water, containing in solution or suspension the 
substances whose action was to be observed. 

Water-Culture has recently contributed so much to oar 
knowledge of the conditions of vegetable growth, that 
some account of the mode of conducting it may be prop- 
erly given in this place. Cause a num- 
ber of seeds of the plant it is desired to 
experiment upon to germinate in moist 
blotting-paper, and, when the roots have 
become an inch or two in length, select 
the strongest seedlings, and support 
them so that the roots shall be immersed 
in water, while the seeds themselves 
shall be just above the surface of the 
liquid. 

For this purpose, in case of a single 
maize plant, for example, provide a 
quart cylinder or bottle with a wide 
mouth, to which a cork is fitted, as in 
Fig. 22. Cut a vertical notch in the 
cork to its center, and fix therein the 
stem of the seedling by packing with 
cotton. The cork thus serves as a sup- 
port of the plant. Fill the jar with pure 
water to such a height that when the 
cork is brought to its place, the seed, S, 
shall be a little above the liquid. If 
the endosperm or cotyledons dip into the water, they 
will speedily mould and rot ; they require, however, to be 
kept in a moist atmosphere. Thus arranged, suitable 
warmth, ventilation, and illumination alone are requi- 
site to continue the growth until the nutriment of the seed 




Fig. 23. 



182 HOW CROPS GROW. 

is nearly exhausted. As regards illumination, this should 
be as full as possible, for the foliage ; but the roots should 
be protected from it, by enclosing the vessel in a shield of 
black paper, as, otherwise, minute parasitic algae would 
in time develop upon the roots, and disturb their functions. 
For the first days of growth, pure distilled water may ad- 
vantageously surround the roots, but, when the first green 
leaf appears, they should be placed in the solution whose 
nutritive power is to be tested. The temperature should 
be properly proportioned to the light, in imitation of what 
is observed in the skillful management of conservatory or 
house-plants. 

The experimenter should first learn how to produce 
large and well-developed plants by aid of an appropriate 
liquid, before attempting the investigation of other prob- 
lems. For this purpose, a solution or mixture must be 
prepared, containing in proper proportions all that the 
plant requires, save what it can derive from the atmos- 
phere. The experience of Nobbe and Siegert, Knop, 
Wolff, and others,* supplies valuable information on this 
point. Wolff has obtained striking results with a variety 
of plants in using a solution made essentially as follows: 

Place 20 grams of the fine powder of well-burned bones 
with a half pint of water in a large glass flask, heat to boil- 
ing, and add nitric acid cautiously in quantity just suffi- 
cient to dissolve the bone-ash. In order to remove any 
injurious excess of nitric acid, pour into the boiling liq- 
uid a solution of pure potassium carbonate until a slight 
permanent turbidity is produced; then add 11 grams of 
potassium nitrate, 7 grams of crystallized magnesium sul- 
phate, and 3 grams of potassium chloride, with water 
enough to make the solution up to the bulk of one liter. 

Wolff's solution, thus prepared, contains in 1000 parts 
as follows, exclusive of iron: 



* See especially Tollens (Henneberg's Jour, fur Landwirthschaft, 1882, p. 
537) for full and concise instructions. 



THE ASH OF PLANTS. 183 

Phosphoric acid 8.2 

Lime 10.5 

Potash 9.1 

Magnesia 1.4 

Sulphuric acid 2.2 

Chlorine 0.9 

Nitric acid 29.7 

Solid Matters 62 

Water 938 

1000 

For use, dilute 15 or 20 c. c. of the above solution with 
water to the bulk of a liter anct add one or two drops of 
strong solution of ferric chloride. 

The solution should be changed at first every week, and, 
as the plants acquire greater size, their roots should be 
transferred to a larger vessel filled with solution of the 
same strength, and the latter changed every 5 or 3 days. 

It is important that the water which escapes from the 
jar by evaporation and by transpiration through the plant 
should be daily or oftener replaced, by filling it with pure 
water up to the original level. The solution, whose prep- 
aration has been described, may be turbid from the sepa- 
ration of a little calcium sulphate before the last dilution, 
as well as from the precipitation of phosphate of iron on 
adding ferric chloride. The former deposit may be dis- 
solved, though this is not needful; the latter will not dis- 
solve, and should be occasionally put into suspension by 
stirring the liquid. When the plant is half grown, fur- 
ther addition of iron is unnecessary. 

In this manner, and with this solution, Wolff produced 
a maize plant five and three quarters feet high, and equal 
in every respect, as regards size, to plants from similar 
seed, cultivated in the field. The ears were not, however, 
fully developed when the experiment was interrupted by 
the plant becoming unhealthy. 

With the oat his success was better. Four plants were 
brought to maturity, having 46 stems and 1535 well-de- 
veloped seeds. (Vs. St., VIII, pp.190-215.) 



184 HOW CEOPS GROW. 

In similar experiments, Nobbe obtained buckwheat 
plants, six to seven feet high, bearing three hundred 
plump and. perfect seeds, and barley stools with twenty 
grain-bearing stalks. (Vs. St., VII, p. 72.) 

In water -culture the composition of the solution is suf- 
fering continual alteration, from the fact that the plant 
makes, to a certain extent, a selection of the matters pre- 
sented to it, and does not necessarily absorb them in the 
proportions in which they originally existed. In this 
way, disturbances arise which impede or become fatal to 
growth. In the early experiments of Sachs and Knop, 
in 1860, they frequently observed that their solutions 
suddenly acquired the odor of hydrogen sulphide, and 
black iron sulphide formed upon the roots, in consequence 
of which they were shortly destroyed. This reduction of 
a sulphate to a sulphide takes place only in an alkaline 
liquid, and Stohmann was the first to notice that an acid 
liquid might be made alkaline by the action of living 
roots. The plant, in fact, has the power to decompose 
salts, and by appropriating the acids more abundantly 
than the bases, the latter accumulate in the solution in 
the free state, or as carbonates with alkaline properties. 

To prevent the reduction of sulphates, the solution 
must be kept slightly acid, if needful, by addition of a 
very little free nitric acid, and, if the roots blacken, they 
must be washed with a dilute acid, and, after rinsing with 
water, must be transferred to a fresh solution. 

On the other hand, Kiihn has shown that when am- 
monium chloride is employed to supply maize with nitro- 
gen, this salt is decomposed, its ammonia assimilated, and 
its chlorine, which the plant cannot use, accumulates in 
the solution in the form of hydrochloric acid to such an 
extent as to prove fatal to the plant (Henneberg's Journal, 
1864, pp. 116 and 135). Such disturbances are avoided by 
employing large volumes of solution, and by frequently 
renewing them. 



THE ASH OF PLANTS. 185 

The concentration of the solution is by no means a 
matter of indifference. While certain aquatic plants, as 
sea-weeds, are naturally adapted to strong saline solutions, 
agricultural land-plants rarely succeed well in water cul- 
ture", when the liquid contains more than y^^ of solid 
matters, and will thrive in considerably weaker solutions. 

Simple well-water is often rich enough in plant-food to 
nourish vegetation perfectly, provided it be renewed suffi- 
ciently often. Sachs's earliest experiments were made 
with well-water. 

Birner and Lucanus, in 1864 ( Vs. St.,Ylll, 154), raised 
oat-plants in well-water, which in respect to entire weight 
were more than half as heavy as plants that grew simul- 
taneously in garden soil, and, as regards seed-production, 
fully equalled the latter. The well-water employed con- 
tained but stjW °f dissolved matters, or in 100,000 parts: 

Potash 2.10 

Lime 15.10 

Magnesia 1.50 

Phosphoric acid 0.16 

Sulphuric acid 7.50 

Nitric acid 0.00 

Silica, Chlorine, Oxide of iron traces 

Solid Matters 32.36 

Water 99,967.64 

100,000 

On the other hand, too great dilution is fatal to growth. 
Kobbe (Vs. St., VIII, 337) found that in a solution con- 
taining but to otto - °f s °lid matters, which was continually 
renewed, barley made no progress beyond germination, 
and a buckwheat plant, which at first grew rapidly, was 
soon arrested in its development, and yielded but a few 
ripe seeds, and but 1.746 grm. of total dry matter. 

While water-culture does not provide all the normal 
conditions for the growth of land plants^ — the soil having 
important functions that cannot be enacted by any liquid 
medium — it is a method of producing highly-developed 
plants, under circumstances which admit of accurate con- 



186 HOW CROPS GROW. 

trol and great variety of alteration, and is, therefore, of 
the utmost value in vegetable physiology. It has taught 
important facts which no other means of study could re- 
veal, and promises to enrich our knowledge in a still 
more eminent degree. 

Potassium, Calcium, and Magnesium as soluble 
Salts, Phosphorus as Phosphates and Sulphur as 
Sulphates, are absolutely necessary for the life of 
Agricultural Plants, as is demonstrated by all the ex- 
periments hitherto made for studying their influence. 

It is impossible to recount here in detail the evidence 
to this effect that is furnished by the investigations of 
Salm-Horstmar, Sachs, Knop, Nobbe, Birner and Luca- 
nus, and others ( Vs. St., VIII, p. 128-161). 

Some of the experimental proof of this statement is 
strikingly exhibited by the figures on Plate I, copied 
from Nobbe, showing results of the water-culture of 
buckwheat in normal nutritive solutions and in solutions 
variously deficient. 

Is Sodium Essential for Agricultural Plants? 
This question has occasioned much discussion. A glance 
at the table of ash-analyses (pp. 164-170) will show that 
the range of variation is very great as regards this alkali- 
metal. The older analysts often reported a considerable 
proportion of sodium oxide, even 20% or more, in the ash 
of seeds and grains. In most of the analyses, however, 
sodium oxide is given in much smaller quantity. The 
average in the ashes of the grains is less than 3 per cent, 
and in not a few of the analyses it is entirely wanting. 

In the older analyses of other classes of agricultural 
plants, especially in root crops, similarly great variations 
occur. Some uncertainty exists as to these older data, for 
the reason that the estimation of sodium by the processes 
customarily employed is liable to great inaccuracy, espe- 
cially with the inexperienced analyst. On the one hand, 
it is not or was not easy to detect, much less to estimate, 



THE ASH OF PLANTS. 187 

minute traces of sodium when mixed with much potassi- 
um ; while, on the other hand, sodium, if present to the 
extent of a per cent or more, is very liable to be estimated 
too high. It has therefore been doubted if these high 
percentages in the ash of grains are correct. 

Again, tbe processes formerly employed for preparing 
the ash of plants for analysis were such as, by too elevated 
and prolonged heating, might easily occasion a partial 
or total expulsion of sodium from a material which prop- 
erly should contain it, and we may hence be in doubt 
whether the older analyses, in which sodium is not men- 
tioned, are to be altogether depended upon. 

The later analyses, especially those by Bibra, Zoeller, 
Arendt, Bretschneider, Ritthausen, and others, who have 
employed well-selected and carefully-cleaned materials for 
their investigations, and who have been aware of all the 
various sources of error incident to such analyses, must 
therefore be appealed to in this discussion. From these 
recent analyses we are led to precisely the same conclu- 
sions as were warranted by the older investigations. Here 
follows a statement of the range of percentages of sodium 
oxide in the ash of several field crops, according to the 
newest analyses: 

SODIUM OXIDE (SODA) IN LATER ASH-ANALYSES. 
Ash of Wheat kernel, none, Bibra, to 5% Bibra. 

» " " 0.28% Lawes& Gilbert," 1.18% 

" Potato tuber, none, { gSorff, " 4% W ° lff " 

" Barlev kernel I X % nibra, u m ,( Bibra. 

uaney Kernel, j 2% teller, b % \ Veltmann. 
' " " " 7% Zoeller. 

ii o 1)rai . bppt I 4% Ritthausen, " 29.8% Ritthausen. 

»u & ar Deei, { 7 ^ Bretschneider, " 16.6% Bretschneider. 

'« Turnip root, 7.7% Anderson, " 17.1% Anderson. 

Although, as just indicated, sodium in some instances 
has been found wanting in the wheat kernel and in po- 
tato tubers, it is not certain that it was absent from other 
parts of the same plants, nor has it been proved that 
sodium is wanting in any entire plant which has grown 
on a natural soil. 



188 HOW CROPS GROW. 

Weinhold found in the ash of the stem and leaves of 
the common live-for-ever (Sedum telephium) no trace of 
sodium detectable by ordinary means ; while in the ash 
of the roots of the same plant there occurred 1.8 per 
cent of its oxide ( Vs. St, IV, p. 190). 

It is possible then that, in the above instances, so- 
dium really existed in the plants, though not ' in those 
parts which were subjected to analysis. It should be 
added that in ordinary analyses, where sodium is stated 
to be absent, it is simply implied that it is present, if at 
all, in too small a quantity to admit of determining by 
the usual method, while in reality a minute amount may 
be present in all such cases.* 

The final result of all the analytical investigations 
hitherto made, with regard to cultivated agricultural 
plants, then, is that sodium is an extremely variable in- 
gredient of the ash of plants, and though generally pres- 
ent in some proportion, and often in large proportion, 
has been observed to be absent in weighable quantity in 
the seeds of grains and in the tubers of potatoes. 

Salm-Horstmar, Stohmann, Knop, and Nobbe & Sie- 
gert have contributed experimental evidence bearing on 
this question. 

The investigations of Salm-Horstmar were made with 
great nicety, and especial attention was bestowed on the 
influence of very minute quantities of the various sub- 
stances employed. He gives as the result of numerous 
experiments, that, for wheat, oats, and barley, in the 
early vegetative stages of growth, Sodium, while advan- 
tageous, is not essential, but that for the perfection of 
fruit an appreciable though minute quantity of this ele- 
ment is indispensable. ( Versuche unci Resultate fiber 
die Nalirung der Pflanzen, pp. 12, 27, 29, 36.) 



*The methods of spectral analysis, by which sTnrrrornnn! of a gram of 
sodium oxide may be detected, demonstrate this element to be so uni- 
versally distributed that it is next to impossible to find or to prepare 
anything that is free from it. 



THE ASH OF PLANTS. 180 

Stohmann's single experiment led to the similar con- 
clusion, that maize may dispense with sodium in the 
earlier stages of its growth, but requires it for a full 
development. (Henneberg^s Jour, far Landivirthschaft, 
1862, p. 25.) 

Knop, on the other hand, succeeded in bringing the 
maize plant to full perfection of parts, if not of size, in a 
solution which was intended and asserted to contain no 
sodium. (Vs. St., Ill, p. 301.) Nobbe & Siegert came 
to the same results in similar trials with buckwheat. 
Vs. St., IV, p. 339.) 

Later trials by Nobbe, Schroder and Erdmann, and by 
others, confirm the conclusion that sodium may be nearly 
or altogether dispensed with by plants. 

The buckwheat represented in Plate I vegetated for 3 
months in solutions as free as possible from sodium, with 
the exception of VI, in which sodium was substituted 
for potassium. 

The experiments of Knop, Nobbe, Siegert and others, 
while they prove that much sodium is not needful to 
maize and buckwheat, do not, however, satisfactorily 
demonstrate that a little sodium is not necessary, because 
the solutions in which the roots of the plants were im- 
mersed stood for months in glass vessels, and could 
scarcely fail to dissolve some sodium from the glass. 
Again, slight impurity of the substances which were em- 
ployed in making the solution could scarcely be avoided 
without extraordinary precautions, and, finally, the seeds 
of these plants might originally have contained enough 
sodium to supply this substance to the plants in appre- 
ciable quantity. 

To sum up, it appears from all the facts before us : 

1. That sodium is never totally absent from plants, 
and that, 

2. If indispensable, but a minute amount of it is 
requisite. 



190 HOW CHOPS GROW. 

3. That the foliage and succulent portions of the plant 
may include a considerable amount of sodium that is not 
necessary to the plant ; that is, in other words, accidental. 

Can Sodium replace Potassium? — The close simi- 
larity of potassium and sodium, and the variable quanti- 
ties in which the latter especially is met with in plants, 
have led to the assumption that one of these alkali-metals 
can take the place of the other. 

Salm-Horstmar and Knop & Schreber fir^t demon- 
strated that sodium cannot entirely take the place of 
potassium — that, in other words, potassium is indispen- 
sable to plant life. Plate I, VI, shows the development 
of buckwheat during 3 months, in Nobbe, Schroder & 
Erdmann's water-cultures, when, in a normal nutritive 
solution, potassium is substituted by sodium, as com- 
pletely as is practicable. 

Cameron concluded, from a series of experiments which 
it is unnecessary to describe, that, under natural condi- 
tions, sodium nni y partially replace potassium. A partial 
replacement of this, kind would appear to be indicated 
by many facts. Thus, Herapath has made two analyses 
of asparagus, one of the wild, the other of the culti- 
vated plant, both gathered in flower. The former was 
rich in sodium, the latter almost destitute of this sub- 
stance, but contained correspondingly more potassium. 
Two analyses of the ash of the beet, one by Wolff (1), the 
other by Way (2), exhibit similar differences : 

Asparaaus. Field Beet. 

Wild. Cultivated. 1. 2. 

Potassium oxide 18.8 50.5 57.0 25.1 

Sodium oxi de 1G.2 trace 7.3 34.1 

Calcium oxide 28.1 21.3 5.8 2.2 

Magnesium oxide 1.5 4.0 2.1 

Chlorine 16.5 8.3 4.9 34.8 

Sulphur trioxide 9.2 4.5 3.5 3.6 

Phosphorus pentoxide 12.8 12.4 12.9 1.9 

Silica 1.0 3.7 3.7 1.7 

These results go to show — it being assumed that only a 
very minute amount of sodium, if any, is absolutely nee- 



THE ASH OF PLANTS. 191 

essary to plant-life — that the sodium which appears to 
replace potassium is accidental, and that the replaced 
potassium is accidental also, or in excess above what is 
really needed by the plant, and leaves us to infer that the 
quantity of these bodies absorbed depends to some ex- 
tent on the composition of the soil, and is to the same 
degree independent of the wants of vegetation. 

Alkalies in Strand and Marine Plants. — The 
above conclusions apply also to plants which most com- 
monly grow near or in salt water. Asparagus, the beet 
and carrot, though native to saline shores, are easily ca- 
pable of inland cultivation, and indeed grow wild in com- 
parative absence of sodium compounds. 

The common saltworts, Salsola, and the samphire, 
Salicomia, are plants which, unlike those just men- 
tioned, seldom stray inland. Grdbel, who has analyzed 
these plants as occurring on the Caspian steppes, found 
in the soluble part of the ash of the Salsola brachiata 
4.8 per cent of potassium oxide, and 30.3 per cent of 
sodium oxide, and in the Salicomia lierbacea 2.6 per 
cent of potassium oxide and 36.4 per cent of sodium 
oxide, the sodium oxide constituting in the first instance 
no less than -^ and in the latter ^ of the entire 
weight, not of the ash, but of the air-dry plant. Potas- 
sium is never absent from th'ese forms of vegetation. 
(Agricultur- Chemie, 3te Auf., p. 66.) 

According to Cadet (Liebig's Emahrung der Veg., 
p. 100), the seeds of the Salsola kali, sown in common 
garden soil, gave a plant which contained both sodium 
and potassium ; from the seeds of this, sown also in 
garden soil, grew plants in which only potassium-salts 
with traces of sodium could be found. These strand- 
plants are occasionally found at a distance front salt- 
shores, and their growth as strand-plants appears to be 
due to their capacity for flourishing in spite of salt, and 
not from their requiring it. (Hoffmann, Vs. St., XIII, 
p. 295.) 



192 HOW CROPS GROW. 

Another class of plants — the sea-weeds (algce) — de- 
rive their nutriment exclusively from the sea-water in 
which they are immersed. Though the quantity of po- 
tassium in sea-water is but 3^ that of the sodium, it is 
yet a fact, as shown by the analyses of Forchhammer 
{Jour, fur Prakt. CJhem., 36, p. 391) and Anderson 
(Trans. High, and Ag. Soc, 1855-7, p. 349) that the 
ash of sea- weeds is, in general, as rich, or even richer, in 
potassium than in sodium. In 14 analyses, by Forch- 
hammer, the average amount of sodium in the dry weed 
was 3.1 per cent; that of potassium 2.5 per cent. In 
Anderson's results the percentage of potassium is inva- 
riably higher than that of sodium.* 

Analogy with land-plants would lead to the inference 
that the sodium of the sea-weeds is in a great degree ac- 
cidental. In fact, Fucus vesiculosis and Zygogonium sal- 
inum have been observed to nourish in fresh water. 
(Vs. St., XIII, p. 295.) r 

Iron is Essential to Plants. — It is abundantly 
proved that a minute quantity of ferric oxide, Fe 2 8 , is 
essential to growth, though the agricultural plant may 
be perfect if provided with so little as to be discoverable 
in its ash only by sensitive tests. According to Salm- 
Horstmar, ferrous oxide, FeO, is indispensable to the 
colza plant. ( Versuche, etc., p. 35.) Knop asserts that 
maize, which refuses to grow in entire absence of iron, 
nourishes when ferric phosphate, which is exceedingly 
insoluble, is simply suspended in the solution that bathes 
its roots for the first four weeks only of the growth of 
the plant. (Vs. St., V, p. 101.) 

We find that the quantity of ferric oxide given in the 
analyses of the ashes of agricultural plants is small, being 
usually less than one per cent. 

Here, too, considerable variations are observed. In 



♦Doubtless due to the fact that the material used by Anderson was 
freed by washing from adhering common salt. 



THE ASH OF PLANTS. 193 

the analyses of the seeds of cereals, ferric oxide ranges 
from an unweighable trace to 2 and even 3%. In root 
crops it has been found as high as 5%. Kekule found 
in the ash of gluten from wheat 7.1% of ferric oxide. 
(Jahresbericht der Chem., 1851, p. 715.) Schulz-Fleeth 
found 17.5% in the ash of the albumin from the juice of 
the potato tuber. The proportion of ash is, however, so 
small that in case of potato-albumin the ferric oxide 
amounts to but 0. 12 per cent of the dry substance. (Der 
Rationelle Ackerbau, p. 82.) 

In the ash of wood, and especially in that of bark, ferric 
oxide often exists to the extent of 5 to 10%. The. largest 
percentages have been found in aquatic plants. In the 
ash of the duckweed (Lemna trisulca) Liebig found 
7.4%. Gorup-Besanez found in the ash of the leaves of 
the Trapa natans 29.6%, and in the ash of the fruit- 
envelope of the same plant 68.6%. (Ann. Ch. Ph., 118, 
p. 223.) 

Probably much of the iron of agricultural and land 
plants is accidental. In case of the Trapa natans, we 
cannot suppose all the iron to be essential, because the 
larger share of it exists in the tissues as a brown powdery 
oxide which may be extracted by acids, and has the ap- 
pearance of having accumulated there mechanically. 

Doubtless a portion of the iron encountered in anal- 
yses of agricultural vegetation has never once existed 
within the vegetable tissnes, but comes from the soil, 
which adheres with great tenacity to all parts of plants. 

Manganese is Unessential to Agricultural Plants. 
Manganese is commonly much less abundant than iron, 
and is often, if not usually, as good as wanting in agri- 
cultural plants. It generally accompanies iron where 
the latter occurs in considerable quantity. Thus, in the 
ash of Trapa, the oxide Mn 3 4 was found to the extent 
of 7.5-14.7%. Sometimes it is found in much larger 
quantity than oxide of iron ; e. g.. G. Fresenius found 
13 



194 HOW CROPS GROW. 

11.2% of oxide of manganese in ash of leaves of the red 
beech {Fagus sylvatica) that contained but 1% of oxide 
of iron. In the ash of oak leaves (Quercus robur) Neu- 
bauer found, of the former 6.6, of the latter but 1.2%. 

In ash of the wood of the larch (Larix Europma), Bot- 
tinger found 13.5% Mn 3 4 and 4.2% Fe 2 3 , and in ash 
of wood of Pinus sylvestris 18.2% Mn 3 4 , and 3.5% 
Fe 2 3 . In ash of the seed of colza, Nitzsch found 16.1% 
Mn 3 4 , and 5.5 Fe 2 3 . In case of land plants, these 
high percentages are accidental, and specimens of most 
of the plants just named have been analyzed, which were 
free from all but traces of oxide of manganese. 

Salm-Horstmar concluded from his experiments that 
oxide of manganese is indispensable to vegetation. 
Sachs, Knop, and most other experimenters in water- 
culture, make no mention of this substance in the mix- 
tures, which in their hands have served for the more or 
less perfect development of a variety of agricultural 
plants. Birner & Lucanus have demonstrated that man- 
ganese is not needful to the oat-plant, and cannot take 
the place of iron. ( Vs. St., VIII, p. 43.) 

Is Chlorine Indispensable to Crops ? — What has 
been written of the occurrence of sodium in plants ap- 
pears to apply in most respects equally well to chlorine. 
In nature, sodium is generally associated with chlorine 
as common salt. It is most probably in this form that 
the two substances usually enter the plant, and in the 
majority of cases, when one of them is present in large 
quantity, the other exists in corresponding quantity. 
Less commonly, the chlorine of plants is in combination 
with potassium exclusively. 

Chlorine is doubtless never absent from the perfect 
agricultural plant, as produced under natural conditions, 
though its quantity is liable to great variation, and is 
often very small — so small as to be overlooked, except by 
the careful analyst. In many analyses of grain, chlorine 



THE ASH OF PLANTS. 195 

is not mentioned. Its absence, in many cas^s, is due, 
without doubt, to the fact that chlorine is readily dissi- 
pated from the ash of substances rich in phosphates or 
silica, on prolonged exposure to a high temperature. In 
some of the later analyses, in which the vegetable sub- 
stance, instead of being at once burned to ashes, at a 
high red heat, is first charred at a heat of low redness, 
and then leached with water, which dissolves the chlo- 
rides, and separates them from the unburned carbon and 
other matters, chlorine is invariably mentioned. In the 
tables of analyses, the averages of chlorine are undeni- 
ably too low. This is especially true of the grains. 

The average of chlorine in the 26 analyses of wheat by 
Way and Ogston,p. 150, is but 0.08%, it not being found 
at all in the ash of 21 samples. In Zoeller's later anal- 
yses chlorine is found in every instance, and averages 
0.7%. In Lawes and Gilbert's numerous analyses of 
wheat-grain ash chlorine ranges from to 1.14%, the 
average being 0.1%. In wheat-straw ash they found 
from 1.08 to 2.06%. The ash was in all cases prepared 
by burning at a low red heat. 

Like sodium, chlorine is particularly abundant in the 
stems and leaves of those kinds of vegetation which grow 
in soils or other media containing much common salt. It 
accompanies sodium in strand and marine plants, and, in 
general, the content of chlorine of any plant may be large- 
ly increased or diminished by supplying it to or withhold- 
ing it from the roots. 

As to the indispensableness of chlorine, we have some- 
what conflicting data. Salm-Horstmar believed that a 
trace of it is needful to the wheat plant, though many of 
his experiments in reference to this element were unsatis- 
factory to himself. Nobbe and Siegert, who have made 
an elaborate investigation on the nutritive relations of 
chlorine to buckwheat, were led to conclude that while 
the stems and foliage of this plant are able to attain a 



19G HOW CROPS GROW. 

considerable development in the absence of chlorine (the 
minute amount in the seed itself excepted), presence of 
chlorine is essential to the perfection of the fruit. 

Leydhecker came to the same conclusions as Nobbe 
and Siegert regarding the indispensableness of chlorine 
to the perfection of buckwheat. ( Vs. St., VIII, p. 177.) 

On the other hand, Knop excludes chlorine from the 
list of necessary ingredients of maize, buckwheat, cress, 
and Psamma arenaria, having obtained a maize plant 3 
feet high, bearing 4 ripe seeds, harvested 23 " chlorine- 
free seeds" from 5 buckwheat-plants, and raised 40 to 50 
ripe seeds from more than one cress-plant, all grown 
without chlorine. ( Vs. St., XIII, p. 219.) 

Wagner also obtained, in absence of chlorine, maize- 
plants 40 inches high, of 20 grams dry-weight. One of 
these ripened 5 small seeds, of which two were proved 
capable of germination ; but none of these plants produced 
any pollen and they were fertilized with pollen from 
garden-plants. ( Vs. St., XIII, pp. 218-222.) 

From a series of experiments in water-culture, Birner 
and Lucanus (Vs. St., VIII, p. 160) conclude that chlo- 
rine is not indispensable to the oat-plant, and has no spe- 
cific effect on the production of its fruit. Chloride of 
potassium increased the weight of the crop, chloride of 
sodium gave a larger development of foliage and stem, 
chloride of magnesium was positively deleterious, under 
the conditions of their trials. 

Lucanus (Vs. St., VII, pp. 363-71) raised clover by 
water-culture without chlorine, the crop (dry) weigh- 
ing in the most successful experiments 240 times as much 
as the seed. Addition of chlorine gave no better result. 

Nobbe (Vs. St., VIII, p. 187) has produced normally 
developed vetch and pea plants, but only in solutions 
containing chlorine. Beyer (Vs. St., XI, p. 262) found 
exclusion of chlorine in water-culture to prevent forma- 
tion of seed in case of peas ; the plants, after a month's 



THE ASH OF PLANTS. 197 

healthy growth, produced new shoots only at the expense 
of the older leaves. In similar trials oats gave a small 
crop of ripe seeds when chlorine was not supplied. 
When, however, the seeds thus obtained nearly free from 
chlorine were vegetated in a solution destitute of this 
element they failed to produce seed again, though their 
growth and reproduction were normal when chlorine 
was furnished them in the nutritive solution. 

In Plate I, X shows the extent to which, in Nobbe's 
cultures, buckwheat developed when vegetating for 3 
months in a solution destitute of chlorine, but otherwise 
fully adapted to nourish plants. 

In view of all the evidence, then, it would appear 
probable that chlorine is needful for the cereals, and 
that when the seed and nutritive media (soil or solution 
and air) are entirely destitute of this element fruit cannot 
be perfected. It is probable that in the cases where 
fruit was produced in supposed absence of chlorine this 
substance in some way gained access to the plants. 

Until further more decisive results are reached, we 
are warranted in adopting, with regard to chlorine as 
related to agricultural plants, the following conclu- 
sions, viz. : 

1. Chlorine is never totally absent. 

2. If indispensable, but a minute amount is requisite 
for a very considerable vegetative development. 

3. Some plants, as vetches and peas, require a not in- 
considerable amount of chlorine for full development, 
especially of seed. 

4. The foliage and succulent parts may include a 
large quantity of chlorine that is not indispensable to 
the life of the plant. 

Silica is not indispensable to Plants. — The numer- 
ous analyses we now possess indicate that this substance 
is always present in the ash of all parts of agricultural 
plants, when they grow in natural soil*. 



198 HOW CROPS GROW. 

In the ash of the wood of trees, it usually ranges from 
1-3%, but is often found to the extent of 10-20%, or 
even 30%, especially in the pine. In leaves, it is usually 
more abundant than in stems. The ash of turnip leaves 
contains 3-10% ; of tobacco leaves, 5-18% ; of the oat, 
11-58%. (Arendt, Norton.) In ash of lettuce, 20% ; of 
beech leaves, 26% ; in those of oak, 31% have been 
observed. (Wicke, Henneberg's Jour., 1862, p. 156.) 

The bark or cuticle of many plants contains an extra- 
ordinary amount of silica. The cauto tree of South 
America (Hirtella silicea) is most remarkable in this 
respect. Its bark is very firm and harsh, and is difficult 
to cut, having the texture of soft sandstone. It yields 
34% of ash, and of this 96% is silica. (Wicke, loc. cit., 
p. 143.) 

Another plant, remarkable for its content of silica, is 
the bamboo. The ash of the rind contains 70%, and in 
the joints of the stem are often found concretions of 
hydrated silica, the so-called Tabasldr. 

The ash of the common scouring rush (Equisetum hye- 
male) has been found to contain ^7.5% of silica. The 
straw of the cereal grains, and the stems and leaves of 
grasses, both belonging to the botanical family Orami- 
nacce, are specially characterized by a large content of 
silica, ranging from 40-70% of the ash. The sedge and 
rush families likewise contain much of this substance. 

The position of silica in the plant would thus appear 
to be, in general, at the surface. Although it is present 
in other parts of the plant, yet the cuticle is usually rich- 
est, especially where the content of silica is large. Davy, 
in 1799, drew attention to the deposition of silica in the 
cuticle of the grasses and cereals, and advanced the idea 
that it serves these plants an office of support similar to 
that enacted in animals by the bones. 

In case of the pine (Pinus sylvestris), Wittstein has 
obtained results which indicate that the age of wood or 



THE ASH OF PLANTS. 199 

bark greatly influences the content of silica. He found 
in ash of the — 

Wood of a tree, 220 years old, 32.5% 
" " 170 " 24.1 

" " 135 " 15.1 



And in — 



Bark " 220 " 30.3 

M tc 170 <« 14>4 



" " 135 " 11.9 

In the ash of the straw of the oat, Arendt found the 
percentage of silica to increase as the plant approached 
maturity. So the leaves of forest trees, which in autumn 
are rich in silica, are nearly destitute of this substance 
in spring time. 

Silica accumulates then, in general, in the older and 
less active parts of the plant, whether these be external 
or internal, and is relatively deficient in the younger and 
really growing portions. This rule is not without excep- 
tions. Thus, the chaff of wheat, rye and oats is richer 
in silica than any other part of these plants, and Bottin- 
ger found the seeds of the pine richer in silica than the 
wood. 

In numerous instances, silica is deposited in or upon 
the cell-wall in such abundance that when the organic 
matters are destroyed by burning, or removed by sol- 
vents, the form of the cell is preserved in a silicious 
skeleton. This has long been known in case of the 
Equisetums and Deutzias. Here the peculiar rough- 
nesses of the stems or leaves are fully incrusted or inter- 
penetrated by silica, and the ashes of the cuticle present 
the same appearance under the microscope as the cuticle 
itself. 

The hairs of nettles, hemp, hops, and other rough- 
leaved plants, are highly silicious. 

According to Wicke, the beech owes the smooth and 
undecayed surface which its trunk presents, to the silica 
of the bark. The best textile materials, which are bast- 



200 HOW CROPS GROW. 

fibers of various plants, viz., common hemp, Manila 
hemp (Musa textilis), aloe-hemp (Agave Americana), 
common flax, and New Zealand flax (Phormium tenax) 
are incrusted with silica. In jute (Corchorus textilis) 
some cells are partially incrusted. The cotton fiber is 
free from silica. Wicke (loc. cit. ) suggests that the du- 
rability of textile fibers is to a degree dependent on their 
content of silica. 

Sachs, in 1862, was the first to publish evidence that 
silica is not a necessary ingredient of maize. He ob- 
tained in his early essays in water-culture a maize plant 
of considerable development, whose ashes contained but 
0.7% of silica. Shortly afterwards, Knop produced a 
maize plant with 140 ripe seeds, and a dry-weight of 50 
grammes (nearly 2 oz. av. ) so free from silica that a 
mere trace of this substance could be found in the root, 
but half a milligramme in the stem, and 22 milligrammes 
in the 15 leaves and sheaths. It was altogether absent 
from the seeds. The ash of the leaves of this plant thus 
contained but 0.54 per cent of silica, and the stem but 
0.07 per cent. Way & Ogston had found in the ash of 
field-grown maize, leaf and stem together, 27.98 per 
cent of silica.- 

In the numerous experiments that have been made 
more recently upon the growth of plants in aqueous solu- 
tions, by Sachs, Knop, Nobbe & Siegert, Stohmann, 
Rautenberg & Kuhn, Birner & Lucanus, Leydhecker, 
Wolff, and Hampe, silica, in nearly all cases, has been 
excluded, so far as it is possible to do so, in the use of 
glass vessels. This has been done without prejudice to 
the development of the plants. Nobbe & Siegert and 
Wolff especially have succeeded in producing buckwheat, 
maize, and the oat, in full perfection of size and parts, 
with this exclusion of silica. 

Wolff (Vs. St., VIII, p. 200) obtained in the ash of 
maize thus cultivated, 2 to 3% of silica, while the same 



THE ASH OF PLANTS. 201 

two varieties from the field contained in their ash 11£ to 
13%. The proportion of ash was essentially the same in 
both cases, viz., about 6%. Wolffs results with the oat 
plant were entirely similar. 

Birner & Lucanus ( Vs. St., VIII, p. 141) found that 
the supply of soluble silicates to the oat made its ash very 
rich in silica (40%) but diminished the growth of straw, 
without affecting that of the seed, as compared with 
plants nearly destitute of silica. 

It is thus made certain that plants ordinarily rich in 
silica may attain a high development in absence of this 
substance. We shall see later, however (p. ), that 
silica is probably not altogether useless to plants when 
they grow under ordinary conditions. 

Jodin reports having bred maize by water-culture, with 
the utmost practicable exclusion of silica, for four gener- 
ations — whereby this substance was reduced to the merest 
traces— without interference with the normal develop- 
ment of the plant. (Ann. Agron., IX, p. 385.) 

The Ash-Ingredients, which are Indispensable 
to Crops, may be taken up in Larger Quantity than 
is Essential.— More than eighty years ago, Saussure de- 
scribed a simple experiment which is conclusive on this 
point. He gathered a number of peppermint plants, and 
in some determined the amount of dry matter, which 
was 40.3 per cent. The roots of others were then im- 
mersed in pure water, and the plants were allowed to veg- 
etate %\ months in a place exposed to air and light, but 
sheltered from rain. 

At the termination of the experiment, the plants, 
which originally weighed 100, had increased to 216 parts, 
and the dry matter of these plants, which at first was 
40.3, had become 62 parts. The plants could have 
acquired from the glass vessels and pure water no con- 
siderable quantity of mineral matters. It is plain, then, 
that the ash-inoredients which were contained in two 



202 HOW CROPS GROW. 

parts of the peppermint were sufficient for the produc- 
tion and existence of three parts. We may assume, 
therefore, that at least one-third of the ash of the origi- 
nal })lants was in excess, and accidental. 

The fact of excessive absorption of essential ash-ingre- 
dients is also demonstrated by the precise experiments of 
Wolff on buckwheat, already described (see p. 164), 
where the point in question is incidentally alluded to, 
and the difficulties of deciding how much excess may 
occur, are brought to notice. (See also pp. 192 and 194 
n regard to potassium and iron. ) 

As further striking instances of the influence of the 
nourishing medium on the quantity of ash-ingredients in 
the plant, the following are adduced, which may serve to 
put in still stronger light the fact that a plant does not 
always require what it contains. 

Nobbe & Siegert have made a comparative study of 
the composition of buckwheat, grown on the one hand in 
garden soil, and on the other in an aqueous solution of 
saline matters. (The solution contained magnesium 
sulphate, calcium chloride, phosphate and nitrate of 
potassium, with phosphate of iron, which together con- 
stituted 0.316% of the liquid.) The ash-percentage was 
much higher in the water-plants than in the garden- 
plants, as shown by the subjoined figures. ( Vs. St., V, 
p. 132.) 

Per cent of ash in 

Stems and leaves. Boots. Seeds. Entire plant. 

Water-plant 18.6 15.3 2.6 16.7 

Garden-plant 8.7 6.8 2.4 7.1 

We have seen that well-developed plants contain a 
larger proportion of ash than feeble ones, when they 
grow side by side in the same medium. In disregard of 
this general rule, the water-plant in the present instance 
has an ash-percentage double that of the land-plant, 
although the former was a dwarf compared with the lat- 
ter, yielding but £ as much dry matter. The seeds, how- 
ever, are scarcely different in composition. 



THE ASH OF PLANTS. 203 

Similar results were obtained by Councler with the 
leaves of Acer negundo (Vs. St., XXIX, p. 242), 1,000 
parts of the perfectly dry leaves contained : 

Water-plant. Soil-plant. 

Silica, SiOj, 8.51 23.72 

Sulphuric oxide, S0 3 , 38.97 9.69 

Phosphoric oxide, P 2 5 ,. ..26.00 4.56 

Iron oxide, Fe a 3 , 1.94 1.22 

Magnesium oxide, MgO,. .. 7.56 6.25 

Calcium oxide, CaO, 31.77 36.17 

Sodium oxide, Na 2 0, 1.23 0.88 

Potassium oxide, K 2 0, 96.92 45.05 

212.90 127.54 

Leaves of the water-plant are much richer in ash -ingre- 
dients, especially in sulphate and phosphate of potassium. 
Those of the soil-plant contain more silica and lime. 

Disposition by the Plant of Excessive or Super- 
fluous Ash-ingredients. — The ash-ingredients taken 
up by a plant in excess beyond its actual wants may be 
disposed of in three ways. The soluble matters — those 
soluble by themselves, and also incapable of forming in- 
soluble combinations with other ingredients of the plant 
— viz., the alkali chlorides, sulphates, carbonates, and 
phosphates, the chlorides of calcium and magnesium, 
may— 

1. Eemain dissolved in, and diffused throughout, the 
juices of the plant ; or, 

2. May exude upon the surface as an efflorescence, and 
be washed off by rains. 

Exudation to the surface has been repeatedly observed 
in case of cucumbers and other kitchen vegetables, grow- 
ing in the garden, as well as with buckwheat and barley 
in water-culture. (Vs. St., VI, p. 37.) 

Saussure found in the white incrustations upon cucum- 
ber leaves, besides an organic body insoluble in water and 
alcohol, calcium chloride with a trace of magnesium 
chloride. The organic substance so enveloped the cal- 
cium chloride as to prevent deliquescence of the latter. 
(Recherche* sur la Veg., p. 265.) 



20-4 HOW CROPS GROW. 

Saussure proved that foliage readily yields up saline 
matters to water. He placed hazel leaves eight success- 
ive times in renewed portions of pure water, leaving them 
therein 15 minutes each time, and found that by this 
treatment they lost ^ of their ash-ingredients. The 
portion thus dissolved was chiefly alkaline salts ; but con- 
sisted in part of earthy phosphates, silica, and oxide of 
iron. (Recherches, p. 287.) 

Ritthausen has shown that clover which lies exposed to 
rain after being cut may lose by washing more than one- 
half of its ash-ingredients. 

Mulder (Chemie der Ackerkriime, II, p. 305) attributes 
to loss by rain a considerable share of the variations in 
percentage and composition of the fixed ingredients of 
plants. We must not, however, forget that all the exper- 
iments which indicate great loss in this way have been 
made on the cut plant, and their results may not hold 
good to the same extent for uninjured vegetation. 

3. The insoluble matters, or those which become so in 
the plant, viz., the calcium sulphate, the oxalates, phos- 
phates, and carbonates of calcium and magnesium, the 
oxides of iron and manganese, and silica, may be depos- 
ited as crystals or concretions in the cells, or may incrust 
the cell-walls, and thus be set aside from the sphere of 
vital action. 

In the denser and comparatively juiceless tissues, as in 
bark, old wood, and ripe seeds, we find little variation in 
the amount of soluble matters. These are present in 
large and variable quantity only in the succulent organs. 

In bark (cuticle), wood, and seed envelopes (husks, 
shells, chaff) we often find silica, the oxides of iron 
and manganese, and calcium carbonate — all insoluble 
substances — accumulated in considerable amount. In 
bran, phosphate of magnesium exists in comparatively 
large quantity. In the dense teak wood, concretions of 
calcium phosphate have been noticed. Of a certain 



THE ASH OF PLANTS. 



205 



species of cactus (Cactus senilis) 80% of the dry 
matter consists of crystals of calcium oxalate and phos- 
phate. 

That the quantity of matters thus segregated is in some 
degree proportionate to the excess of them in the nourish- 
ing medium in which the plant grows has been observed 
by Nobbe & Siegert, who remark that the two portions 
of buckwheat, cultivated by them in solutions and in gar- 
den-soil respectively (p. 203), both contained crystals 
and globular crystalline masses, consisting probably of 
calcium and magnesium oxalates, and phosphates, depos- 
ited in the rind and pith ; but that these were by far most 
abundant in the water-plants whose ash-percentage was 
tivicc as great as that of the garden-plants. 

These insoluble substances may be either entirely unes- 
sential, or, having once served the wants of the plant, may 
be rejected as no longer useful, and by assuming the in- 
soluble form, are removed from the sphere of vital action, 
and become in reality dead matter. They are, in fact, 
excreted, though not, in general, 
formally expelled beyond the limits 
of the plant. They are, to some 
extent, thrown off into the bark 
or into the older wood or pith, 
or else are encysted in the living 
cells. 

The occurrence of crystallized salts 
thus segregated in the cells of plants 
is illustrated by the following cuts. 
Fig. 23 represents a crystallized con- 
cretion of calcium oxalate, having a basis or skeleton of 
cellulose, from a leaf of the walnut. (Payen, Chimie In- 
dustrielle, PI. XII.) Fig. 24 shows a mass of crystals of the 
same salt, from the leaf stem of rhubarb. Fig. 25 illus- 
trates similar crystals from the beet root. In the root of 
the young bean. Sachs found a ring of cells, containing 



3KE3C_5 




Fi£. 23. 



206 



HOW CHOPS GKOW. 




crystals of sulphate of lime. (Sitzungsberichte derWien. 

Akad., 37, p. 106.) Bailey ob- 
served in certain parts of the in- 
ner bark of the locust a series of 
cells, each of which contained a 
crystal. In the onion-bulb, and 
many other plants, crystals are 
Fig. 34. Fig. 35. abundant> [Gray's Botanical 

Text-Booh, 6th ed., Vol. II, p. 52.) 

Instances are not wanting in which there is an obvious 
excretion of mineral matters, or at least a throwing of 
them off to the surface. Silica, as we have seen, is often 
found in the cuticle, but is usually imbedded in the cell- 
wall. In certain plants, other substances accumulate in 
considerable quantity without the cuticle. A striking ex- 
ample is furnished by Saxifraga crustata, a low European 
plant, which is found in lime soils. 
The leaves of this saxifrage are en- 
tirely coated with a scaly incrusta 
tion of calcium and magnesium 
carbonates. At the edges of the 
leaf this incrustation acquires a 
considerable thickness, as is illus- 
trated by figure 26, a. In an anal- 
ysis made by Unger, to whom these 
facts are due, the fresh (undried) 
leaves yielded to a dilute acid 
4.14% of calcium carbonate, and 
0.82% of magnesium carbonate. 

Unger learned by microscopic 
investigation that this excretion 
of carbonates proceeds mostly from a series of granular 
expansions at the margin of the leaf, which are directly 
connected with the sap-ducts of the plant. {Sitzungsbe- 
richte der Wien. Akad., 43, p. 519.) 

In figure 26, a represents the appearance of a leaf, magnified 4£ cliam- 




Fig. 36, 



THE ASH OF PLANTS. 20? 

eters. Around the borders are seen the scales of carbonates; some of 
these have been detached, leaving round pits on the surface of the leaf : 
c, d exhibit the scales themselves, e in profile : b shows a leaf, freed 
from its incrustation by an acid, and from its cuticle by potash-solution, 
so as to exhibit the veins (ducts) and glands, whose course the carbon- 
ates chiefly take, in their passage through the plant . 

Further as to the state of ash-ingredients. — It is 
by no means true that the ash-ingredients always exist in 
plants in the forms under which they are otherwise famil- 
iar to us. 

Arendt and Hellriegel have studied the proportions of 
soluble and insoluble matters, the former in the ripe oat 
plant, and the latter in clover at various stages of growth. 

Arendt extracted from the leaves and stems of the oat 
plant, after thorough grinding, the whole of the soluble 
matters by repeated washings in water.* He found that 
all the sulphuric acid and all the chlorine were soluble. 
Nearly all the phosphoric acid was removed by water. 
The larger share of the calcium, magnesium, sodium and 
potassium compounds was soluble, though portions of each 
escaped solution. Iron was found in both the soluble and 
insoluble state. In the leaves, iron was found among the 
insoluble matters after all phosphoric acid had been re- 
moved. Finally, silica was mostly insoluble, though in 
all cases a small quantity occurred in the soluble condi- 
tion, viz., 3-8 parts in 10,000 of the dry plant. ( Wach- 
sthum cler Haferpflanze, pp. 168, 183-4. See, also, table 
on p. 171). 

Weiss and "Wiesner discovered by microchemical in- 
vestigation that iron exists as insoluble ferrous and ferric 
compounds both in the cell-membrane and in the cell- 
contents. (Sitzungsberichte der Wiener A had., 40, 278.) 

Hellriegel found that in young clover a larger propor- 
tion of the various bases was soluble than in the mature 
plant. As a rule, the leaves gave most soluble matters, 
the leaf stalks less, and the stems least. He obtained, 



*To extract the soluble parts of the grain in this way was impossible. 



208 HOW CROPS GROW. 

among others, the following results ( Vs. St., IV, 
p. 59) : 

Of 100 parts of the following fixed ingredients of clover, 
were dissolved in the sap, and not dissolved — 

In young leaves. In full-grown leaves. 

Potash (dissolved 75.2 37.3 

^ otasn \ undissolved 24.8 62.7 

T . Q (dissolved G9.5 724 

lame \ undissolved 30.5 27.6 

Mn^Psia (dissolved 43.6 78.3 

magnesia... J undissolved 56.4 21.7 

Phosphoric (dissolved 20.9 19.9 

oxide, P 2 Og { undissol ved 79.1 80.1 

c . 1 . (dissolved 26-8 16.1 

feinca \ undissolved 73.2 83.9 

These researches demonstrate that potassium and sodi- 
um — bodies, all of whose commonly-occurring compounds, 
silicates excepted, are readily soluble in water — enter into 
insoluble combinations in the plant ; while phosphoric 
acid, which forms insoluble salts with "calcium, magnesi- 
um, and iron, is freely soluble in connection with these 
bases in the sap. 

It should be added that sulphates may be absent from 
the plant or some parts of it, although they are found in 
the ashes. Thus, Arendt discovered no sulphates in the 
lower joints of the stem of oats after blossom, though in 
the upper leaves, at the same period, sulphuric oxide 
(S0 3 ) formed nearly 7% of the sum of the fixed ingre- 
dients. (Wachsthum der Haferpf., p. 157.) Ulbricht 
found that sulphates were totally absent from the lower 
leaves and stems of red clover, at a time when they were 
present in the upper leaves and blossom. ( Vs. St. , IV. , p. 
30 Tabslle. ) Botli Arendt and Ulbricht observed that sul- 
phur existed in all parts of the plants they experimented 
upon ; in the parts just specified, it was, however, no 
longer combined to oxygen, but had, doubtless, become 
an integral part of some albuminoid or other complex or- 
ganic body. Thus the oat stem, at the period above cited, 
contained a quantity of sulphur, which, had it been con- 
verted into sulphuric oxide, would have amounted to 14% 



THE ASH OF PLANTS. 209 

of the fixed ingredients. In the clover leaf, at a time 
when it was totally destitute of sulphates, there existed 
an amount of sulphur which, in the form of sulphuric 
oxide, would have made 13.7% of the fixed ingredients, 
or one per cent of the dry leaf itself.* 

Other ash-ingredients.— Salm-Horstmarhas describ- 
ed some experiments, from which he infers that a minute 
amount of Lithium and Fluorine (the latter as fluoride 
of potassium) are indispensable to the fruiting of barley. 
(Jou v. fa rprakt. Chem. , 84. p . 140. ) The same observer, 
some years ago, was led to conclude that a trace of Titan- 
ium is a necessary ingredient of plants. The later re- 
sults of water-culture would appear to demonstrate that 
these conclusions are erroneous. 

The rare alkali-metal, Rubidium, has been found in the 
sugar-beet, in tobacco, coffee, tea, and the grape. It doubt- 
less occurs, perhaps together with the similar Caesium in 
many other plants, though always in very minute quan- 
tity. Birner and Lucanus found that these bodies, in the 
absence of potassium, acted as poisons to the oat. ( Vs. 
St., VIII, p. 147.) 

According to Nobbe, Schroeder and Erdmann, Lith- 
ium is very injurious to buckwiieat, even in presence of 
potassium. When lithium was substituted for two- 
thirds of the potassium of a normal nutritive solution, 
buckwheat vegetated indeed for 3 months, the stem 
reaching a length of 18 inches, but the plant was small 
and unhealthy, the leaves were pale and the older ones 
dropped away, as shown by VIII, plate I. (Vs. St., 
XIII, p. 356). 

*Arendt was the first to estimate sulphuric oxide (SO s ) in vegetable 
matters with accuracy, and to discriminate it from the sulphur of or- 
ganic compounds. This chemist separated the sulphates of the oat- 
plant by extracting the pulverized material with acidulated water. He 
likewise estimated the total sulphur by a special method, and by sub- 
tracting the sulphur of the sulphuric oxide from the total he obtained as 
a difference that portion of sulphur which belonged to the albuminoids, 
etc. In his analysis of clover. Ulbrieht followed a similar plan. (Vs. St., 
Ill, p. 147.) As has already been stated, many of the older analyses are 
wholly untrustworthy as regards sulphur and sulphuric oxide. 
14 



210 HOW CROPS GROW. 

The investigations of A. Braun and of Risse (Sachs, 
Exp. Physiologie, 153) show that Zinc is a usual ingredi- 
ent of plants growing about zinc-mines, where the soil 
contains carbonate or silicate of this metal. Certain 
marked varieties of plants are peculiar to, and appear to 
have been produced by, such soils, viz., a violet ( Viola 
tricolor, var. calaminaris), and a shepherd's purse 
(Thlaspi alpestre, var. calaminaris). In the ash of the 
leaves of the latter plant, Risse found 13% of oxide of 
zinc ; in other plants he found from 0.3 to 3.3%. These 
plants, however, grow equally well in absence of zinc, 
which may slightly modify their appearance, but is unes- 
sential to their nutrition. 

Boron as boric acid has recently been found in many 
wines of California and Europe. 

Copper is often or commonly found in the ashes of 
plants ; and other elements, viz;, Arsenic, Barium and 
Lead, have been discovered therein, but as yet we are not 
warranted in assuming that any of these substances are 
of importance to agricultural vegetation. The soluble 
compounds of copper, arsenic and lead are in fact very 
injurious to plant life, unless very highly diluted. 

Iodine, an invariable and probably a necessary constit- 
uent of many algae, is not known to exist to any consid- 
erable extent or to be essential in any cultivated plants. 

§4. 

FUNCTIONS OF THE ASH-INGREDIENTS. 

Although much has been written, little is certainly 
known, with reference to the subject of this section. 

Sulphates. — The albuminoids, which contain sulphur 
as an essential ingredient, obviously cannot be produced 
in absence of sulphates, which, so far as we know, are the 
exclusive source of sulphur to plants. The sulphurized 



THE ASH OF PLANTS. 211 

oils of the onion, mustard, horse-radish, turnip, etc., like- 
wise require sulphates for their organization. 

Phosphates. — The phosphorized substances (prota- 
gon, lecithin, chlorophyl) require to their elaboration that 
phosphates be at the disposal of the plant. Knop has shown 
that hypophosphites cannot take the place of phosphates. 
The albuminoids which are probably formed in the foliage 
must pass thence through the cells and ducts of the stem 
into growing parts of the plant, and into the seed, where 
they accumulate in large quantity. But the albuminoids 
penetrate membranes with great difficulty and slowness 
when in the pure state. The di- and tri-potassic phosphates 
dissolve or form water-soluble compounds with many 
albuminoids, and, according to Schumacher (Physik der 
Pjianze, p. 128), considerably increase the diffusive rate 
of these bodies, and thus facilitate their translocation in 
the plant. 

Potassium. — The organic acids, viz., oxalic, malic, 
tartaric, citric, etc., require potassium to form the salts 
of this metal, which exist abundantly in plants, e. g. , 
potassium oxalate in sorrel, potassium bitartrate in the 
grape, potassium malate in garden rhubarb; and without 
potassium it is in most cases probably impossible for the 
acids to accumulate or to be formed. Mercadante culti- 
vated sorrel (Oxalis acetosella and Rnmex acetosa), in ab- 
sence of potassium-salts; sodium, calcium, and magnesium 
being supplied. The plants failed to fructify, and their 
juices contained but one-eighth as much free acid (or acid 
salts?) as exists in the sap of the same kind of plants veg- 
etating under normal conditions. The acids — oxalic, with 
a little tartaric — were united to calcium (Berichte, 1875, 
II, p. 1200). The organic acids may result from the de- 
composition of carbhydrates (starch or sugar), or they 
may be preliminary stages in the production of the carb- 
hydrates. In either case their formation is an index to 
the constructive processes by which the plant originates 



212 HOW CROPS GROW. 

new vegetable substance and increases in dry weight. 
Mercadante's observations are therefore in accord with the 
results of the investigations next to be considered. 

In 1869, Nobbe, Schroder, and Erdmann employed the 
method of water-culture to make an elaborate study of 
the influence of potassium on the vegetative processes, 
and found that, all other needful conditions of growth 
being supplied, in absence of potassium buckwheat 
plants vegetated for three months without any increase in 
weight — that is to say, without producing new vegetable 
matter. Examination of these miniature plants demon- 
strated that (in absence of potassium) the first evident 
stage in the production of vegetable substance, viz., the 
appearance of starch in the cldorophyl granules of the 
leaf, could not be attained. The experimenters therefore 
drew the conclusion that potassium is an essential factor 
in the assimilation of carbon and the formation of starch. 
They found that the plants were able to produce starch 
when potassium was supplied either as -chloride, nitrate, 
phosphate or sulphate. The transfer of the starch from 
the leaves to the fruit, or its conversion into a soluble 
form, appeared to require the presence of chlorine ; ac- 
cordingly, potassium chloride gave the best developed 
plants, especially at the period of fructification. This 
conclusion was greatly strengthened by the observation, 
repeatedly made, that the miniature plants which had 
vegetated for three or four weeks without increase of 
weight* or growth other than that which the seedling can 
make at the expense of the seed, began at once, on suit- 
able addition of potassium chloride to the nutritive solu- 
tion, to form starch, discoverable in all the chlorophyl 
granules, and thenceforward developed new stems and 
leaves and grew in quite the normal manner. In Plate 
I the appearance of some of the plants produced in these 
trials is shown. la represents the average plant raised 
in the normal solution containing abundance of potas- 



PLATE I. 

explanation. (See p. 212.) 

Water-cultures of Japanese Buckwheat, supplied with the ingre- 
dients of a Normal Solution, viz. : Sulphates, Nitrates, Phosphates and 
Chlorides of Potassium, Magnesium, Calcium andiron, except as stated 
below. 

I and la. Solution normal. Potassium as Chloride. 

II. Solution without Potassium. 

II 3 . Without Potassium for 4 weeks, thereafter Potassium Chloride. 

III. Potassium as Nitrate. Chlorine as in Normal. 

IV. Potassium as Sulphate. Chlorine one-fourth of Normal. 

V. Potassium as Phosphate. Chlorine one-fifth of Normal. 

VI. Sodium but not Potassium. 

VIII. Lithium. 

IX. Without Calcium. 

X. Without Chlorine. 
XL Without Nitrogen. 

The meter-scale (39| inches) serves to measure the dimensions of the 
plants. 



THE ASH OF PLANTS. 21 3 

sium chloride. II was deprived of potassium save that 
contained in the seed. In IV and V, respectively, the 
chlorine of the solution was reduced to one-fourth and 
one-fifth the amounts contained in the normal solution 
and replaced by sulphuric acid in IV and by phosphoric 
acid in V. In case of II 3 , the plant vegetated without 
potassium for four weeks with a result similar to II, and 
then for two months was supplied with potassium chlo- 
ride. For numerous interesting details reference must 
be made to the original paper ( Vs. St., XIII, pp. 
321-424). 

Liipke, from water-cultures witli the flowering bean 
Phaseolus multiflorus, and common bean P. vulgaris, 
has recently arrived at different conclusions. He finds 
that these plants are able, under the utmost possible ex- 
clusion of potassium, to assimilate carbon and produce 
starch, in fact to grow and to carry on all the vegetative 
functions that belong to the fully-nourished plant, 
though on a diminished scale. In order to limit the 
supply of potassium to the utmost, the cotyledons of some 
of the plants were cut away when the plumule began to 
appear above them. In this way 90% of the potassium 
of the seed was removed* and while the plants were 
thereby reduced in dimensions, their power to vegetate 
in a healthy manner was not suppressed. After 65 days 
of vegetation one of these plants yielded a crop of dry- 
substance 4.8 times as much as was contained in the 
newly sprouted seedling after excision of the cotyledons. 

Some results of these cultures are shown in Plate II. 
The stem of the unmutilated flowering bean in normal 
solution I, a, reached a final length of 80 inches, that de- 
prived of potassium grew to 40 inches. 

Nobbe's conclusion that potassium is specifically essen- 
tial or concerned in starch-production is accordingly erro- 

* Liipke found that one seed of P. multiilorus contained 23 milligrams 
of potassium oxide; the seedling, after cutting off the cotyledons, con- 
tains 2.:? mm. 



214 HOW CROPS GROW. 

neons. As Liipke remarks, potassium is rather like nitro- 
gen, phosphorus, sulphur, etc., one of the elements of 
which probably a cercain quantity is indispensable to the 
formation of every vegetable cell. Nobbe's results per- 
haps indicate that buckwheat requires relatively more 
potassium than the bean for its processes of growth. 
{Land. Jahrbuoher, 1888, pp. 887-913.) 

Calcium. — Bohm (Jahresbericht ilber Ag. Chemie, 
1875-6, Bd. I, p. 255) and Von Raumer ( Vs. St., XXIX, 
251) have furnished evidence that calcium (lime) is di- 
rectly necessary to the formation of cell-tissue, that is to 
say, of cellulose. 

This evidence rests upon observations made with seed- 
lings of the flowering bean (scarlet-runner), Phaseolus 
multiflorus. When a seed sprouts, the young plant at first 
is nourished exclusively by the nutritive matters contained 
in the seed. When its roots enter the soil it begins to de- 
rive water, nitrogen, and ash-ingredients from the earth. 
When its leaves unfold in the light it begins to gather 
carbon from the air and to increase in weight. If its 
roots are placed in pure water it can acquire no ash-in- 
gredients ; if its leaves are kept in darkness it can gain 
nothing from the air. Thus circumstanced, it may live 
and vegetate for a time, but constantly loses in total dry 
weight, and its apparent growth is only the formation of 
new parts at the expense of the old. For some days the 
young stem shoots upward without green color, but per- 
fectly formed, and then (in case of the flowering bean) 
suddenly, at a little space below the terminal bud, a dis- 
coloration appears, the stem wilts, withers, and. dies 
away. The growth of stem that thus occurs is accom- 
panied by and depends upon the solution of starch in the 
seed-lobes and its transfer to the points of growth where 
it is made over into cellulose — the frame- work of the 
stem. In absence of any external source of ash-ingredi- 
ents the young stem dies long before the starch of the 



THE ASH OF PLANTS. 215 

cotyledons is consumed. But if the roots be placed in 
a nutritive solution suited to water-culture, the stem 
grows on without injury until the cotyledons are com- 
pletely emptied of starch, and afterwards continues to de- 
velop at the expense of the lower leaves. 

The arrest of growth in the stem evidently is due to 
the absence of some one or more ash-iugredients, and 
Bohm found in fact that, by withholding lime-salts from 
the roots, this characteristic malady was invariably pro- 
duced. Hence he concludes that calcium compounds are 
immediately concerned in the conversion of starch into 
cellulose. 

Magnesium. — Von Raumer,in the paper just referred 
to (Vs. St., XXIX, pp. 263 and 273), gives his observa- 
tions on the relations of the magnesium salts to the veg- 
etative processes. He states that, all other conditions 
being favorable, the exclusion of magnesium from a nu- 
tritive solution in which the scarlet-runner vegetates is 
followed by cessation of chlorophyl-production and of 
that enlargement of the new-formed cells wherein the 
act of growth largely consists. Accordingly, in absence 
of magnesium-supply, the plants, which at first grew nor- 
mally, after reaching a height of forty inches, began to 
show signs of disturbed nutrition. The uppermost in- 
ternodes (joints) of the stems almost cea'sed to lengthen 
and became exceptionally thick and hard, their leaves 
failed to open, and both joints and leaves were white in 
color with but the faintest tint of green. Soon new up- 
ward growth ceased altogether, the terminal bud and 
unfolded leaves dried away, and, while the lower, first- 
formed and green leaves remained fresh for weeks and 
the lower stem threw out new shoots, healthy growth 
was at a stand-still, and the plants gradually withered 
and perished. The normal growth of the bean plants 
for a month or more in nutritive solutions containing no 
magnesium is accounted for by the supply of this ele- 



216 HOW CROPS GROW. 

ment existing in the seed,* which evidently was enough 
for the necessities of growth until the stem was forty 
inches high. From that point on the plants almost 
ceased to grow, and gradually died from want of food 
and inability to assimilate. 

We have already seen that, according to Hoppe-Seyler, 
magnesium is a constant and presumably an essential in- 
gredient of chlorophyllan, a crystallized derivative of 
chlorophyl. This makes evident that magnesium is di- 
rectly concerned in and needful to the formation of the 
chlorophyl granules which, so far as observation as yet 
has gone, are the seat of those operations which first 
construct organic substance from inorganic matter. 

Magnesium and calcium occur in the aleurone of seeds 
and, according to Grubler, form soluble, crystallizable 
compounds with certain albuminoids, so that these ele- 
ments, like potassium, may be concerned in the transport 
of protein-bodies. 

Silica. — Humphrey Davy was the first to suggest that 
the function of silica might be, in case of the grasses, 
sedges, and equisetums, to give rigidity to the slender 
stems of these plants, and enable them to sustain the 
often heavy weight of the fruit. 

The results of the many experiments in water-culture 
by Sachs, Knop* Wolff, and others (see p. 200), in which 
the supply of silica has been reduced to an extremely 
small amount, without detriment to the development of 
plants, commonly rich in this substance, prove in the 
most conclusive manner, however, that silica does not 
essentially contribute to the stiffness of the stem. 

Wolff distinctly informs us that the maize and oat 
plants produced by him, in solutions nearly free from 
silica, were as firm in stalk, and as little inclined to 
lodge or " lay," as those which grew in the field. 

* Common beans contain about one-fourth of one per cent of mag- 
nesia. 



THE ASH OF PLANTS. 217 

The "lodging" of cereal crops is demonstrated to re- 
sult from too close a stand and too little light, which 
occasion a slender and delicate growth, and is not per- 
ceptibly influenced by presence or absence of silica. 
Silica, however, if not necessary to the life of the cereals, 
appears to have an important office in their perfect de- 
velopment under ordinary circumstances. Kreuzhage 
and Wolff have carefully studied the relations of silica to 
the oat plant, using the method of water-culture. In a 
series of nine trials in 1880, where, other things being 
equal, much silica, little silica, and no silica were sup- 
plied, the numbers of seeds produced were 1,423, 1,039, 
and 715 respectively, the corresponding weights being 
46, 34, and 23 grams. The total crops weighed 196, 
172, and 168 grams respectively, so that while the yield 
of seed was doubled in presence of abundant silica, the 
total crop (dry) was increased in weight but one-sixth. 
The supply of silica was accompanied with an absolutely 
diminished root-formation as well as by a relatively in- 
creased seed-production. Similar trials in 1881 and 1882 
gave like results (Vs. St., XXX, p. 161). Wolff con- 
cludes that silica ensures the timely and uniform ripen- 
ing of the crop as well as favors the maximum develop- 
ment of seed. 

The natural supply of silica appears to be always suf- 
ficient. Application of this substance in fertilizers has 
never proved remunerative. In those water-cultures 
where large seed-production has been obtained in ab- 
sence of silica, it is probable that lime-salts, phosphates, 
or other ash-ingredients, which are commonly taken up 
more abundantly than in field culture, have brought 
about the same result that silica usually effects. This 
action of the ash-ingredients is apparently due to a clog- 
ging of the cell-tissues and consequent check of the pro- 
cesses of growth and would seem to be caused either by 
the otherwise unessential silica or bv an excess of the 



218 HOW CROPS GROW. 

ingredients essential to growth. The hard, dense coat of 
the seed of the common weed "stone-crop" (Litkosper- 
mum) usually contains some 13 to 20 per cent of silica 
and twice that amount of calcium carbonate. Hohnel 
produced these seeds in water-culture from well-grown 
plants deprived of silica and found them quite normally 
developed. The seed-coat was permeated with calcium 
carbonate, which appears to have fully replaced silica 
without detriment to the plant (Haberlandt, Unter- 
suchungen, II, p. 160). 

Chlorine. — As has been mentioned, both Nobbe and 
Leydhecker found that buckwheat grew quite well up to 
the time of blossom without chlorides. From that 
period on, in absence of chlorides, remarkable anomalies 
appeared in the development of the plant. In the ordi- 
nary course of growth, starch, which is organized in the 
mature leaves, does not remain in them to much extent, 
but is transferred to the newer organs, and especially to 
the fruit, where it often accumulates in large quantities. 
In absence of chlorides in the experiments of Nobbe and 
Leydhecker, the terminal leaves becam^ thick and fleshy, 
from extraordinary development of cell-tissue, at the 
same time they curled together and finally fell oif, upon 
slight disturbance. The stem became knotty, transpira- 
tion of water was suppressed, the blossoms withered 
without fructification, and the plant prematurely died. 
The fleshy leaves were full of starch-grains, and it ap- 
peared that in absence of chlorine the transfer of starch 
from the foliage to the flower and fruit was rendered im- 
possible ; in other words, chlorine (in combination with 
potassium or calcium) was concluded to be necessary to 
— was, in fact, the agent of — this transfer. 

Knop believes, however, that these phenomena are due 
to some other cause, and that chlorine is not essential to 
the perfection of the fruit of buckwheat (see p. 196). 
Knop (Chem, CentralMatt, 1869, p. 189) obtained some 



THE ASH OF PLANTS. 219 

ripe, well-developed buckwheat seeds in chlorine-free 
water-cultures, while in the same solutions, with addition 
of chlorides, other buckwheat plants remained sterile, 
the flowers withering without setting seed. Knop states 
that in other trials maize and bean plants grew better 
without than with chlorides. In either case starch did 
not accumulate in the stem or leaves of maize, while all 
the organs of the bean were overloaded with starch both 
in presence and absence of chlorides. 

The experiments of Nobbe and Leydhecker are very 
circumstantially described and have been confirmed by 
the later work of Nobbe, Schroder, and Erdmann ( Vs. 
St., XIII, pp. 392-6). See p. 196. 

Iron. — We are in possession of some interesting facts, 
which throw light upon the function of this metal in the 
plant. In case of the deficiency of iron, foliage loses its 
natural green color, and becomes pale or white even in 
the full sunshine. In absence of iron a plant may un ; 
fold its buds at the expense of already organized matters, 
as a potato-sprout lengthens in a dark cellar, or in the 
manner of fungi and white vegetable parasites ; but the 
leaves thus developed are incapable of assimilating carbon, 
and actual growth or increase of total weight is impossi- 
ble. Salm-Horstmar showed (1849) that plants which 
grow in soils or media destitute of iron are very pale in 
color, and that addition of iron-salts very speedily gives 
them a healthy green. Sachs found that maize-seed- 
lings, vegetating in solutions free from iron, had their 
first three or four leaves green ; several following were 
white at the base, the tips being green, and afterward 
perfectly white leaves unfolded. On adding a few drops 
of sulphate or chloride of iron to the nourishing medium, 
the foliage was plainly altered within twenty-four hours, 
and in three to four days the plant acquired a deep, lively 
green. Being afterwards transferred to a solution desti- 
tute of iron, perfectly white leaves were again developed, 






220 HOW CROPS GROW. 

and these were brought to a normal color by addition of 
iron. 

E. Gris was the first to trace the reason of these effects, 
and first found (in 1843) that watering the roots of 
plants with solutions of iron, or applying such solutions 
externally to the leaves, shortly developed a green color 
where it was previously wanting. By microscopic stud- 
ies he found that, in the absence of iron, the protoplasm 
of the leaf-cells remains a colorless or yellow mass, desti- 
tute of visible organization. Under the influence of iron, 
grains of chlorophyl begin at once to appear, and pass 
through the various stages of normal development. We 
know that the power of the leaf to decompose carbon 
dioxide and assimilate carbon resides in the cells that 
contain chlorophyl, or, we may say, in the chlorophyl- 
grains themselves. We understand at once, then, that 
in the absence of iron, which is essential to the forma- 
tion of chlorophyl, there can be no proper growth, no 
increase at the expense of the external atmospheric food 
of vegetation. 

Eisse, under Sachs' s direction {Exp. Physiologie, p. 
143), demonstrated that manganese cannot take the plac3 
of iron in the office just described. 



CHAPTER III. 

QUANTITATIVE RELATIONS AMONG THE INGREDIENTS 

OF PLANTS. 

Various attempts have been made to exhibit definite 
numerical relations between certain different ingredients 
of plants. 

Equivalent Replacement of Bases. — In 1840, Lie- 
big, in his Chemistry applied to Agriculture, suggested 



QUANTITATIVE RELATIONS. 221 

that the various bases or basic metals might displace 
each other in equivalent quantities, i. e., in the ratio of 
their molecular or. atomic weights, and that, were such 
the case, the discrepancies to be observed among analyses 
should disappear, if the latter were interpreted on this 
view. Liebig instanced two analyses of the ashes of fir- 
wood and two of pine-wood made by Berthier and Saus- 
sure, as illustrations of the correctness of this theory. 
In the fir of Mont Breven, carbonate of magnesium was 
present ; in that of Mont La Salle, it was absent. In 
the former existed but half as much carbonate of potas- 
sium as in the latter. In both, however, the same total 
percentage of carbonates was found, and the amount of 
oxygen in the bases was the same in both instances. 

Since the unlike but equivalent quantities of potash, 
lime, and magnesia contain the same quantity of oxy- 
gen, these oxides, in the case in question, really replaced 
each other in equivalent proportions. The same was 
true for the ash of pine-wood, from Allevard and from 
Norway. On applying this principle to other cases it 
has, however, signally failed. The fact that the plant 
can contain accidental or unessential ingredients ren- 
ders it obvious that, however truly such a law as that of 
Liebig may in any case apply to those substances which 
are really concerned in the vital actions, it will be impos- 
sible to read the law in the results of analyses. 

Relation of Phosphates to Albuminoids. — Liebig 
likewise considered, that a definite relation exists be- 
tween the phosphoric acid and the albuminoids of the 
ripe grains. That this relation is not constant is evi- 
dent from the following statement of data bearing on 
the question. In the table, the amount of nitrogen (N), 
representing the albuminoids (see p. 113), found in vari- 
ous analyses of rye and wheat grain, is compared with 
that of phosphoric acid (P 2 5 ), the latter being taken as 
unity. The ratios of P 2 5 to N were found to range as 
follows : 



222 HOW CROPS GEOW. 



P,0 B . N. 



2^5 



In 7 Samples of Rye-kernel by Fehling & Faiszt 1 : 1.97—3.06 

" 11 « " " Mayer 1 : 2.04—2.38 

" 5 " " • " Bibra 1:1.68—2.81 

" 6 " " " Siegert 1:2.35—2.96 

«< 28 " " " the extreme range was from — 1:1.68—3.06 

" 2 " " Wheat-kernel by Fehling & Faiszt 1:2.71—2.86 

" 11 " " " Mayer ..1:1.83—2.19 

" 2 " " " Zoeller 1:2.02—2.16 

" 30 " " " Bibra 1 : 1.87—3.55 

w 6 " " " Siegert 1:2.30—3.33 

" 51 " " " the extreme range was from — 1:1.83—3.55 

Siegert, who collected these data ( Vs. St., Ill, p. 147), 
and who experimented on the influence of phosphatic and 
nitrogenous fertilizers upon the composition of wheat and 
rye, gives as the general result of his special inquiries that 
Phosphoric acid and Nitrogen stand in no constant rela- 
tion to each other. Nitrogenous manures increase the per 
cent of nitrogen and diminish that of phosphoric acid. 

Other Relations. — All attempts to trace simple and 
constant relations between other ingredients of plants, 
viz., between starch and alkalies, cellulose and silica, etc., 
have proved fruitless. 

It is much rather demonstrated that the proportion of 
the constituents is constantly changing from day to day as 
the relative mass of the individual organs themselves un- 
dergoes perpetual variation. 

In adopting the above conclusions it is not asserted that 
such genetic relations between phosphates and albumin- 
oids, or between starch and alkalies, as Liebig first sug- 
gested and as various observers have labored to show, do 
not exist, but simply that they do not appear from the 
analyses of plants. 

§2. 

THE COMPOSITION" OF THE PLANT IN SUCCESSIVE STAGES 

OF GROWTH. 

We have hitherto regarded the composition of the plant 
mostly in a relative sense, and have instituted no com par- 



COMPOSITION IN SUCCESSIVE STAGES. 223 

isons between the absolute quantities of its ingredients at 
different stages of growth. We have obtained a series of 
isolated views of the chemistry of the entire plant, or of 
its parts at some certain period of its life, or when placed 
under certain conditions, and have thus sought to ascer- 
tain the peculiarities of these periods, and to estimate the 
influence of these conditions. It now remains to attempt 
in some degree the combination of these sketches into a 
panoramic picture — to give an idea of the composition 
of the plant at the successive steps of its development. 
We shall thus gain some insight into the rate and manner 
of its growth, and acquire data that have an important 
bearing on the requisites for its perfect nutrition. For 
this purpose we need to study not only the relative 
(percentage) composition of the plant and of its parts at 
various stages of its existence, but we must also inform 
ourselves as to the total quantities of each ingredient at 
these periods. 

We shall select from the data at hand those which 
illustrate the composition of the oat-plant. Not only the 
ash-ingredients, but "also the organic constituents, will be 
noticed so far as our information and space permit. 

The Composition and Growth of the Oat-Plant 
may be studied as a type of an important class of agricul- 
tural plants, viz. : the annual cereals — plants which com- 
plete their existence in one summer, and which yield a 
large quantity of nutritious seeds — the most valuable re- 
sult of culture. The oat-plant was first studied in its 
various parts and at different times of development by 
Prof. John Pitkin Norton, of Yale College. His labori- 
ous research published in 1846 ( Trans. Highland and Ag. 
Soc, 1845-7, also^4m. Jour. ofSci. and Arts, Vol. 3, 1847) 
was the first step in advance of the single and disconnected 
analyses which had previously been the only data of the 
agricultural physiologist. For several reasons, however, 
the work of Norton was imperfect. The analytic meth- 



224 HOW CKOPS GROW. 

ods employed by him, though the best in use at that day, 
and handled by him with great skill, were not adapted to 
furnish results trustworthy in all particulars. Fourteen 
years later, Arendt* at Moeckern, and Bretschneiderf at 
Saarau, in Germany, at the same time, but independently 
of each other, resumed the subject, and to their labors 
the subjoined figures and conclusions are due. 

Here follows a statement of the Periods at which the 
plants were taken for analysis : 

[still closed. 

i«t pprinri I J une 18? Arendt — Three lower leaves unfolded, two upper 

z reiloa j " 19, Bretschneider— Four to five leaves developed. 
9H v vir>/i I June 30, (12 days), Arendt— Shortly before full heading. 
za renoa j „ 2 <d, (io days), Bretschneider— The plants were headed. 
•iA P>ovi ->.i I July 1°' (1° days), Arendt— Immediately after bloom. 
aa reiloa \ « 8, ( 9 days), Bretschneider— Full bloom, 
dti! -p^virwi (July 21. (11 days), Arendt— Beginning to ripen. 
Mnrenouj „ 28, (20 days), Bretschneider— " 

5th Ppriod 1 Jul y 31 ' ( 10 da y s )' Arendt— Fully ripe. 

om i eriou j Augi ^ ^ Q days), Bretschneider— Fully ripe. 

It will be seen that the periods, though differing some- 
what as to time, correspond almost perfectly in regard to 
the development of the plants. It must be mentioned 
that Arendt carefully selected luxuriant plants of equal 
size, so as to analyze a uniform material (see p. 171), 
and took no account of the yield of a given surface of soil. 
Bretschneider, on the other hand, examined the entire 
produce of a square rod. The former procedure is best 
adapted to study the composition of the well-nourished 
individual plant; the latter gives a truer view of the crop. 

The unlike character of the material as just indicated 
is but one of the various causes which might render the 
two series of observations discrepant. Thus, differences 
in soil, weather and seeding, would necessarily influence 
the relative as well as the absolute development of the two 
crops. The results are, notwithstanding, strikingly ac- 
cordant in many particulars. In all cases the roots were 
not and could not be included in the investigation, as it 
is impossible to free them from adhering soil. 

* Das Wachsthum der Hdferpflanze, Leipzig, 1859. 

iWachsthumsverhaltnisse der Haferpflanze, Jour, fur Prakt. Chem.,16, 
193. 



COMPOSITION IN SUCCESSIVE STAGES. 225 

The Total Weight of Crop per English acre, at the 

end of each period, was as follows: 

Table I.—Bretschneider. 
1st Period, 6,358 lbs. avoirdupois. 
2d " 10,603 " " 

3d " 16,623 " " 

4th " 14,981 M " 

5th " 10,622 " " 

The Total Weights of Water and Dry Matter for 

all but the 2d Period — the material of which was acci- 
dentally lost — were: 

Table II.— Bretsclmeider. 

Dry Matter, Water, 

lbs. av. per acre. lbs. av. per acre. 

1st Period, 1,284 5,074 

2d&3d" 4,383 12,240 

4th " 5,427 9,554 

5th " 6,886 3,736 

1. — From Table I it is seen: That the weight of the 
live crop is greatest at or before the time of blossom.* 
After this period the total weight diminishes as it had 
previously increased. 

2. — From Table II it becomes manifest: That the organ- 
ic tissue (dry matter) continually increases in quantity up 
to the maturity of the plant; and 

3. — The loss after the 3d Period falls exclusively upon 
the water of vegetation. At the time of blossom the 
plant has its greatest absolute quantity of water, while 
its least absolute quantity of this ingredient is found when 
it is fully ripe. 

By taking the difference between the weights of any 
two Periods, we obtain: 

The Increase or Loss of Dry Matter and Water 
during each Period. 

Table Ill.—Bretschneider. 

Dry Matter, Water, 

lbs per acre. lbs per acre. 
1st Period, (58 days), 1,284 Gain. 5,074 Gain. 

2d&3d" (19 days), 3,099 " 7,166 " 

4th " (20 days), 1,044 " 2,686 Loss. 

5th " ( 9 days), 1,459 " 5,818 " 



*In Arendt's Experiment, at the time of "heading out," 3d Period. 
15 



2d & 3d " 


163 " 


tt 


377 


4th 


52 " 


it 


134 


5th " 


162 " 


ti 


646 



226 . HOW CROPS GROW. 

On dividing the above quantities by the number of days 
of the respective periods, there results: 

The Average Daily Gain or Loss per Acre during 
each Period. 

Table IV. — Bretschneider . 

Dry Matter. Water. 

1st Period, 22 lbs. Gain. 87 lbs. Gain. 

« 

Loss. 
t< 

4. — Table III, and especially Table IV, show that the 
gain of organic matter in Bretschneider's oat-crop went 
on most rapidly at or before the time of blossom (accord- 
ing to Arendt at the time of heading out). This was, then, 
the period of most active growth. Afterward the rate of 
growth diminished by more than one-half, and at a later 
period increased again, though not to the maximum. 

Absolute Quantities of Carbon, Hydrogen, Oxy- 
gen, Nitrogen (Organic Matter), and Ash in the dry 
oat-crop at the conclusion of the several periods (lbs. 
per acre) : 





TABLE V.- 


—Bretschneider. 








Carbon. 


Hydrogen. 


Oxygen. 


Nitrogen. 


Ash* 


1st Period, 


593 




80 


455 


46 


110 


2d & 3d " 


2,137 




286 


1,575 


122 


263 


4th " 


2,600 




343 


2,043 


150 


291 


5th " 


3,229 




405 


2,713 


167 


372 



Amounts of Carbon, Hydrogen, Oxygen, Nitro- 
gen, and Ash-ingredients assimilated by the oat-crop 
during the several periods. Water of vegetation is not 
included (lbs. per acre) : 

Table VI.— Bretschneider. 



Carbon. 


Hydrogen. 


Oxygen. 


Nitrogen. 


Ash- 


ingredients, 


1st Period, 593 


80 


455 


46 




110 


2d&3d " 1,544 


206 


1,575 


76 




153 


4th " 453 


57 


468 


28 




28 


5th " 629 


62 


670 


17 




81 



*In Bretschneider's analyses, "ash" signifies the residue left after 
carefully burning the plant. In Arendt's investigatton the sulphur 
and chlorine were determined in the unburned plant. 



COMPOSITION IN" SUCCESSIVE STAGES. ^27 

Relative Quantities of Carbon, Hydrogen, Oxy- 
gen, Nitrogen (Organic Matter) and Ash in the dry 
oat-crop, at the end of the several periods (per cent) : 

Table VII.— Bretschneider. 





Carbon. 


Hydrogen. 


Oxygen. 


Nitrogen. 


{Organic Matter.) Ash. 


1st Period, 


46.2? 


6.23 


35.39 


3.59 


91.43 8.57 


2d&3d " 


48.76 


6.53 


35.96 


2.79 


94.04 5.96 


4th " 


47.91 


6.33 


37.65 


2.78 


94.67 5.33 


5th " 


46-89 


5.88 


39.40 


2.43 


94.60 5.40 



Relative Quantities of Carbon, Hydrogen, Oxy- 
gen, and Nitrogen, in dry substance, after deducting 
the somewhat variable amount of ash (per cent) : 

Table YIll.— Bretschneider. 





Carbon. 


Hydrogen. 


Oxygen. 


Nitrogen. 


1st Period, 


50.55 


6.81 


38.71 


3.93 


2d & 3d " 


51.85 


6.95 


38.24 


2.86 


4th " 


50.55 


6.96 


39.83 


2.93 


5th " 


49.59 


6.21 


41.64 


2.56 



5. The Tables V, VI, VII, and VIII, demonstrate that 
■while the absolute quantities of the elements of the dry 
oat-plant continually increase to the time of ripening, 
they do not increase in the same proportion. In other 
words, the plant requires, so to speak, a change of diet 
as it advances in growth. They further show that nitro- 
gen and ash are relatively more abundant in the young 
than in the mature plant ; in other words, the rate of 
assimilation of Nitrogen and fixed ingredients falls be- 
hind that of Carbon, Hydrogen, and Oxygen. Still oth- 
erwise expressed, the plant as it approaches maturity 
organizes relatively more carbhydrates and less albu- 
minoids. 

The relations just indicated appear more plainly when 
we compare the Quantities of Nitrogen, Hydrogen, and 
Oxygen, assimilated during each period, calculated upon 
the amount of Carbon assimilated in the same time and 
assumed at 100. 

T^ble IK— Bretschneicler. 

Carbon. Nitrogen. Hydrogen. Oxygen. 

1st Period, 100 7.8 13.4 73.G 

2d&3d " 100 4.9 13.3 72.5 

4th « 100 6.1 12.3 100.8 

5th " 100 2.6 10.6 106.5 



228 HOW CROPS GROW. 

From Table IX we see that the ratio of Hydrogen to 
Carbon regularly diminishes as the plant matures ; that 
of Nitrogen falls greatly from the infancy of the plant to 
the period of full bloom, then strikingly increases during 
the first stages of ripening, but falls off r at last to mini- 
mum. The ratio of Oxygen to Carbon is the same during 
the 1st, 2d, and 3d Periods, but increases remarkably 
from the time of full blossom until the plant is ripe. 

As already stated, the largest absolute assimilation of 
all ingredients — most rapid growth — takes place at the 
time of heading out, or blossom. At this period all the 
volatile elements are assimilated at a nearly equal rate, 
and at a rate similar to that at which the fixed matters 
(ash) are absorbed. In the first period Nitrogen and 
Ash ; in the 4th Period, Nitrogen and Oxygen ; in the 
5th Period, Oxygen and Ash are assimilated in largest 
proportion. 

This is made evident by calculating for each period the 
relative average daily increase of each ingredient, the 
amount of the ingredients in the ripe plant being assumed 
at 100, as a point of comparison. The figures resulting 
from such a calculation are given in 





Table X.—Bretschneider. 








Carbon. 


Hydrogen. 


Orygen. 


Nitrogen. 


Ash. 


1st Period, 


0.31 


0.33 


0.28 


0.47 


0.50 


2d and 3d " 


2.51 


2.68 


2.17 


2.39 


2.13 


4th " 


0.89 


0.88 


1.07 


1.06 


0.47 


5th 


1.49 


1.16 


1.89 


0.75 


1.70 



The increased assimilation of the 5th over the 4th 
Period is, in all probability, only apparent. The results 
of analysis, as before mentioned, refer only to those parts 
of the plant that are above ground. The activity of the 
foliage in gathering food from the atmosphere is doubt- 
less greatly diminished before the plant ripens, as evi- 
denced by the leaves turning yellow and losing water of 
vegetation. The increase of weight in the plant above 
ground probably proceeds from matters previously stored 



COMPOSITION IN SUCCESSIVE STAGES. 229 

in the roots, which now are transferred to the fruit and 
foliage, and maintain the growth of these parts after 
their power of assimilating inorganic food (C0 2 , H 2 0, 
NH 8 , N 2 5 ) is lost. 

The following statement exhibits the absolute average 
daily increase of Carbon, Hydrogen, Oxygen, Nitrogen, and 
Ash, (kiring the several periods (lbs. per acre) : 





Table Xl.—Bretsch 


neider. 








Carbon. 


Hydrogen. 


Oxygen. 


Nitrogen. 


Ash. 


1st Period, 


10.0 


" 1.4 


7.8 


0.8 


1.9 


2d and 3d " 


81.0 


10.8 


83.0 


4.0 


8.0 


4th * " 


22.6 


2.9 


23.4 


1.4 


1.4 


5th 


70.0 


6.9 


74.4 


1.9 


9.0 



Turning now to Arendt's results, which are carried 
more into detail than those of Bretschneider, we will 
notice: 

A. — The Relative (percentage) Composition of the 
Entire Plant and of its Parts* during the several 
periods of vegetation. 

1. Fiber \ is found in greatest proportion — 40 per cent 
— in the lower joints of the stem, and from the time 
when the grain "heads out," to the period of bloom. 
Kelatively considered, there occur great variations in the 
same part of the plant at different stages of growth. 
Thus, in the ear, which contains the least fiber, the 
quantity of this substance regularly diminishes, not 
absolutely, but only relatively, as the plant becomes 
older, sinking from 27 per cent at heading to 12 per 
cent at maturity. In the leaves, which, as regards 
fiber, stand intermediate between the stem and ear, this 

* Arendt selected large and well-developed plants, divided them into 
six parts, and analvzed each part separately. His divisions of the 
plants were : 1, the three lowest .joints of the stem; 2, the two middle 
joints; 3, the upper joint; 4, the three lowest leaves; 5, the two upper 
leaves; 6, the ear. The stems were cut just above the nodes, the leaves 
included the sheaths, the ears were stripped from the stem. Arendt 
rejected all plants which were not perfect when gathered. When 
nearly ripe, the cereals, as is well known, often lose one or more of 
their lower leaves. For the numerous analyses on which these conclu- 
sions are based we must refer to the original. 

tl. e., Crude cellulose; see p. 45. 



230 HOW CROPS GROW. 

substance ranges from 22 to 38 per cent. Previous to 
blossom, the upper leaves, afterwards the lower leaves, 
are the richest in fiber. In the lower leaves the maxi- 
mum (33 per cent) is found in the fourth ; in the upper 
leaves (38 per cent), in the second period. 

The apparent diminution in amount of fiber is due in 
all cases to increased production of other ingredient. 

2. Fat and Wax are least abundant in the stem. Their 
proportion increases, in general, in the upper parts of the 
stem as well as during the latter stages of its growth. The 
range is from 0.2 to 3 per cent. In the ear the propor- 
tion increases from 2 to 3.7 per cent. In the leaves the 
quantity is much larger and is mostly wax with little fat. 
The smallest proportion is 4.8 per cent, which is found in 
the upper leaves when the plant is ripe. The largest 
proportion, 10 per cent, exists in the lower leaves, at the 
time of blossom. The relative quantities found in the 
leaves undergo considerable variation from one stage of 
growth to another. 

3. Non-nitrogenous matters, other than fiber, viz., starch, 
sugars, gums, etc.,* undergo great and irregular variation. 
In the stem the largest percentage (57 per cent) is found 
in the young lower joints; the smallest (43 per cent) in 
ripe upper straw. Only in the ear occurs a regular in- 
crease, viz., from 54 to 63 per cent. 

4. The albummoids,\ in Arendt's investigation, exhibit 
a somewhat different relation to the vegetable substance 
from what was observed by Bretschneider, as seen from 
the subjoined comparison of the percentages found at 
the different periods : 

PERIODS. 

I. II. III. IV. V. 

Arendt 20.93 11.65 10.86 13.67 14.30 

Bretschneider 22.73 17.67 17.61 15.39 



* What remains after deducting fat and wax, albuminoids, fiber and 
ash, from the dry substance, is here included, 
t Calculated by multiplying the percentage of nitrogen by 6.33. 

These differences may be variously accounted for. They 



COMPOSITION IN SUCCESSIVE STAGES. 



231 



are due, in part, to the fact tliat Arendt analyzed onTy 
large and perfect plants. Bretschneider, on the other 
hand, examined all the plants of a given plot, large and 
small, perfect and injured. The differences illustrate 
what has been already insisted on, viz., that the develop- 
ment of the plant is greatly modified by the circum- 
stances of its growth, not only in reference to its exter- 
nal figure, but also as regards its chemical composition. 

The relative distribution of nitrogen in the parts of the 
plant at the end of the several periods is exhibited by the 
following table, simple inspection of which shows the 
fluctuations (relative) in the content of this element. The 
percentages are arranged for each period separately, pro- 
ceeding from the highest to the lowest : 



PERIODS. 



I. 


II. 


III. 


IV. 


V. 


Upper leaves. 


Lower leaves. 


Upper leaves. 


Ears. 


Ears. 


3.74 


2.39 


2.27 


2.85 


3.04 


Lower leaves. 


Upper leaves. 


Lower leaves. 


Upper leaves. 


Upper leaves. 


3.38 


2.19 


2.18 


1.91 


1.74 


Lower leaves. 


Ears. 


Ears. 


Lower leaves. 


Upper stem. 


2.15 


2.06 


1.85 


1.G2 


1.56 




Middle stem. 


Upper stem. 


Upper stem. 


Lower leaves. 




1.52 


1.34 


1.G0 


1.43 




Upper stem. 


Middle stem. 


Middle stem. 


Middle stem. 




0.87 


0.98 


1.20 


1.17 




Lower stem. 


Lower stem. 


Lower stem. 


Lower stem. 




0.80 


0.88 


0.83 


0.79 



5. Ash. — The agreement of the percentages of ash in 
the entire plant, in corresponding periods of the growth 
of the oat, in the independent examinations of Bret- 
schneider and Arendt, is remarkably close, as appears 



from the figures below 



Bretschneider 8.57 

Arendt 8.03 



II. 



5.24 



PERIODS. 






III. 


IV. 


V. 


5.96 


5.33 


5.40 


5.44 


5.20 


5.17 



As regards the several parts of the plant, it was found 
by Arendt that, of the stem, the upper portion was richest 
in ash throughout the whole period of growth. Of the 
leaves, on the contrary, the lower contained most fixed 
matters. In the ear there occurred a continual decrease 



232 HOW CROPS GROW. 

from its first appearance to its maturity, while in the 
stem and leaves there was, in general, a progressive 
increase towards the time of ripening. The greatest 
percentage (10.5 per cent) was found in the ripe leaves; 
the smallest (0.78 per cent) in the ripe lower straw. 

Far more interesting and instructive than the relative 
proportions are 

B. — The Absolute Quantities of the Ingredients 
found in the Plant at the conclusion of the sev- 
eral periods of growth. — These absolute quantities, 
as found by Arendt, in a given number of carefully- 
selected and vigorous plants, do not accord with those 
obtained by Bretschneider from a given area of ground, 
nor could it be expected that they should, because it is 
next to impossible to cause the same amount of vegeta- 
tion to develop on a number of distinct plots. 

Though the results of Bretschneider more nearly rep- 
resent the crop as obtained in farming, those of Arendt 
give a truer idea of the plant when situated in the best 
possible conditions, and attaining a uniformly high 
development. We shall not attempt to compare the two 
sets of observations, since, strictly speaking, in most 
points they do not admit of comparison. 

From a knowledge of the absolute quantities of the 
substances contained in the plant at the ends of the several 
periods, we may at once estimate the rate of growth, i. e., 
the rapidity with ivhich the constituents of the plant are 
either taken up or organized. 

The accompanying table, which gives in alternate col- 
umns the total iceights of 1,000 plants at the end of the 
several periods, and (by subtracting the first from the 
second, the second from the third, etc.) the gain from 
matters absorbed or produced during each period, will 
serve to justify the deductions that follow', which are 
taken from the treatise of Arendt, and which apply, of 
course, only to the plants examined by this investigator. 



COMPOSITION IN SUCCESSIVE STAGES. 



233 



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234 HOW CROPS GROW. 

1. The plant increases in total weight (dry matter) 
through all its growth, but to unequal degrees in differ- 
ent periods. The greatest growth occurs at the time of 
heading out ; the slowest, within ten days of maturity. 

We may add that the increase of the oat after blossom 
takes place mostly in the seed, the other organs gaining 
but little. The lower leaves almost cease to grow after 
the 2d Period. 

2. Fiber is produced most largely at the time of head- 
ing out (2d Period). When the plant has finished blos- 
soming (end of 3d Period), the formation of fiber 
entirely ceases. Afterward there appears to occur a 
slight diminution of this substance, more probably due 
to unavoidable loss of lower leaves than to a resorption 
or metamorphosis in the plant. 

3. Fat is formed most largely at the time of blossom. 
It ceases to be produced some weeks before ripening. 

4. Albuminoids are very irregular in their formation. 
The greatest amount is organized during the 4th Period 
(after blossoming). The gain in albuminoids within 
this period is two-fifths of the total amount found in the 
ripe plant, and also is nearly two-fifths of the entire gain 
of organic substance in the same period. The absolute 
amount organized in the 1st Period is not much less 
than in the 4th, but in the 2d, 3d and 5th Periods the 
quantities are considerably smaller. 

Bretschneider gives the data for comparing the pro- 
duction of albuminoids in the oat crop examined by him 
with Arendt's results. Taking the quantity found at 
the conclusion of the 1st Period as 100, the amounts 
• gained during the subsequent periods are related as 
follows: 

PERIODS. 

I. II. III. (II. & III.) IV. (II., III. & IV.) V. 

Arendt 100 67 46 (113) 120 (233) 36 

Bretschneider .100 ? ? (165) 62 (227) 35 

We perceive striking differences in the comparison. In 



COMPOSITION IN" SUCCESSIVE STAGES. 235 

Bretschneider's crop the increase of albuminoids goes on 
most rapidly in the 2d and 3d Periods, and sinks rapidly 
during the time when in Arendt's plants it attained the 
maximum. Curiously enough, the gain in the 2d, 3d 
and 4th Periods, taken together, is in both cases as good 
as identical (233 and 227), and the gain during the last 
period is also equal. This coincidence is doubtless, how- 
ever, merely accidental. Comparisons witli other crops 
of oats examined, though much less completely, by 
Stuckhardt (Chemischer Acker smann, 1855) and Wolff 
(Die Ersclwpfang des Bodens dutch die Cultur, 1856) 
demonstrate that the rate of assimilation is not related 
to any special times or periods of development, but 
depends upon the stores of food accessible to the plant 
and the favor of the weather, or other external conditions. 

The following figures, which exhibit for each period 
of both crops a comparison of the gain in albuminoids 
with the increase of the other organic matters, further 
strikingly demonstrate that, in the act of organization, 
the nitrogenous principles have no close quantitative 
relations to the non-nitrogenous bodies (carbhydrates 
and fats). 

The quantities of albuminoids gained during each 
period being represented by 10, the amounts of carbhy- 
drates, etc., are seen from the subjoined ratios : 

PERIODS. 

Ratio in 
I. II & III. IV. V. Ripe Plant. 

Arendt 10:34 10:114 10:28 10: 25 10:66 

Bretschneider..lO : 30 10 : 50 10 : 46 10 : 120 10 : 51 

5. The Ash- ingredients of the oat are absorbed through- 
out its entire growth, but in regularly diminishing quan- 
tity. The gain during the 1st Period being taken at 10, 
that in the 2d Period is 9, in the 3d, 8, in the 4th, 5£, 
in the 5th, 2 nearly. 

The ratios of gain in ash -ingredients to that in entire 
dry substance, are as follows, ash-ingredients being 
assumed as 1, in the successive ^periods : 



236 HOW CROPS GROW. 

1 : 12£, 1 : 27, 1 : 16, 1 : 23, 1 : 19. 

Accordingly, the absorption of ash-ingredients is not 
proportional to the growth of the plant, but is to some 
degree accidental, and independent of the wants of 
vegetation. 

Recapitulation. — Assuming the quantity of each proxi- 
mate element in the ripe plant as 100, it contained at 
the end of the several periods the following amounts 
(per cent) : 







Fiber. 


Fat. 


Carbhydrates.* 


Albuminoids. 


Ash. 


I, 


Period, 


18 


20 


15 


27 


29 


II. 


i« 


81 


50 


47 


45 


55 


III. 


« 


100 


85 


70 


57 


79 


IV. 


« 


100 


100 


92 


90 


95 


V. 


(< 


100 


100 


100 


100 


100 



Taking the total gain as 100, the gain during each 
period was accordingly as follows (per cent) : 

Fiber. Fat. Carbhydrates.* Albuminoids. Ash. 



I. Period, 


18 


20 


15 


27 


29 


II. " 


63 


30 


32 


18 


26 


III. " 


19 


35 


23 


12 


24 


IV. " 





15 


22 


33 


16 


V. " 








8 


10 


5 



100 100 100 100 100 

6. — As regards the individual ingredients of the ash, 
the plant contained at the end of each period the follow- 
ing amounts, — the total quantity in the ripe plant being 
taken at 100. Corresponding results from Bretschneider 
enclosed in ( ) are given for comparison: 



Sulphuric Phosphoric 

Silica. Oxide Oxide Lime. Magnesia. Potash. 

Per cent. Per cent. Per cent. Per cent. Per cent. Per cent. 

I. Period, 18 ( 22) 20 ( 42) 23 ( 23) 30 ( 31) 24 ( 31) 39 ( 42) 

II. m 41j (57) 52) (44) 42j (63) 58j (83) 42 } ( 70 J ( gJ) 

HI. " 70* 52 J 73 > 79) '58* 91 i 

IV. " 93 ( 72) 90 ( 39) 91 ( 74) 99 ( 74) 84 ( 77) 100 (100) 

V. " 100 (100) 100 (100) 100 (100) 100 (100) 100 (100) 100 (95*) 

The gain (or loss, indicated by the minus sign — ) in 
these ash-ingredients during each period is given below: 

* Exclusive of Fiber. 



COMPOSITION IN SUCCESSIVE STAGES. 237 

Sulphuric Phosphoric 







Silica. 


Oxide. 


Oxide. 


Lime. 


Magnesia. 


Potash. 






Per cent. 


. Per cent. 


Per cent. 


Per cent. 


Per cent. 


Per cent. 


I. 


Period 


, 18 ( 22) 


20 ( 42 ) 


23 ( 23) 


30 ( 31 ) 


24 ( 31) 


39 ( 42 ) 


II. 
III. 


<< 

n 


23 [ ( 35) 
29 ) 


■}(.) 


3l) (40) 


28 j ( 52 ) 
21 i 


18 ! ( 42) 
16) 


3 M(47) 
21 J 


IV. 


U 


23 ( 15) 


38 (—5*) 


18 ( 10) 


20 (—9*) 


26 (4 ) 


9 ( 11 ) 


V. 


u 


7 ( 28) 


10 ( 56 ) 


9 ( 27) 


1 ( 17 ) 


16 (23 ) 


(—5*) 






100 (100) 


100 (100) 


100 (100) 


100 (100) 


100 (100) 


100 (100) 



These two independent investigations could hardly 
give all the discordant results observed on comparing 
the above figures, as the simple consequence of the 
unlike mode of conducting them. We observe, for 
example, that in the last period Arendt's plants gathered 
less silica than in any other — only 7 per cent of the 
whole. On the other hand, Bretschneider's crop gained 
more silica in this than in any other single period, viz. : 
28 per cent. A similar statement is true of phosphoric 
oxide, f It is obvious that Bretschneider's crop was tak- 
ing up fixed matters much more vigorously in its last 
stages of growth than were Arendt's plants. As to 
potash, we observe that its accumulation ceased in the 
4th Period in both cases. 

C. — Translocation of Substances in the Plant. 
— The transfer of certain matters from one part of the 
plant to another during its growth is revealed by the 
analyses of Arendt, and since such changes are of inter- 
est from a physiological point of view, we may recount 
them here briefly. 

It has been mentioned already that the growth of the 
stem, leaves, and ear of the oat plant in its later stages 
probably takes place to a great degree at the expense of 
the roots. It is also probable that a transfer of carbhy- 



*In these instances Bretschneider's later crops appear to contain less 
sulphuric oxide, lime and potash, than 1 lie earlier. This result maybe 
due to the washing of the crop by rains, but is probably caused by 
unequal development of the several plots. 

t Phosphoric oxide is the "phosphoric acid," P 2 5 , of older and to a 
great degree of current usage. See p. 163. 



238 HOW CROPS GROW. 

drates, and certain that one of albuminoids, goes on from 
the leaves through the stem into the ear. 

Silica appears not to be subject to any change of posi- 
tion after it has once been fixed by the plant. Chlorine 
likewise reveals no noticeable mobility. 

On the other hand, phosphoric oxide passes rapidly from 
the leaves and stem towards or into the fruit in the ear- 
lier as well as in the later stages of growth, as shown by 
the following figures : 

One thousand plants contained in the various periods 
quantities (grams) of phosphoric oxide as follows : 





1st 


2d 


3d 


4th 


bth 




Period. 


Period. 


Period. 


Period. 


Period. 


3 lower joints of stem x 0.47 


0.20 


0.21 


0.20 


0.19 


2 middle " 


t< 


0.39 


1.14 


0.46 


0.18 


Upper joint 


U 


0.66 


1.73 


0.31 


0.39 


3 lower leaves 


1.05 


0.70 


0.69 


0.51 


0.35 


2 upper leaves 


" 1.75 


1.67 


1.18 


0.74 


0.59 


Ear, 




2.36 


5.36 


10.67 


12.52 



Observe that these absolute quantities diminish in the 
stem and leaves after the 1st or 3d Period in all cases, 
and increase very rapidly in the ear. 

Arendt found that sidphuric oxide existed to a much 
greater degree in the leaves than in the stem through- 
out the entire growth of the oat plant, and that, after 
blossoming, the lower stem no longer contained sulphur 
in the form of sulphates at all, though its total in the 
plant considerably increased. It is almost certain, then, 
that sulphuric oxide originates, either partially or wholly, 
by oxidation of sulphur or some sulphurized compound, 
in the upper organs of the oat. 

Magnesium is translated from the lower stem into the 
upper organs, and in the fruit, especially, it constantly 
increases in quantity. 

There is no evidence that Calcium moves upward in 
the plant. On the contrary, Arendt's analyses go to 
show that in the ear, during the last period of growth, it 



COMPOSITION IN SUCCESSIVE STAGES. 239 

diminishes in quantity, being, perhaps, replaced by 
magnesium. 

As to potassium, no transfer is fairly indicated, except 
from the ears. These contained at blossoming (Period 
III) a maximum of potassium. During their subsequent 
growth the amount of this element diminished, being 
probably displaced by magnesium. 

The data furnished by Arendt's analyses, while they 
indicate a transfer of matters in the cases just named, 
and. in most of them with great certainty, do not and 
cannot from their nature disprove the fact of other simi- 
lar changes, and cannot fix the real limits of the move- 
ments which they point out. 



DIVISION II. 

THE STRUCTURE OF THE PLANT AND 
OFFICES OF ITS ORGANS. 

CHAPTER I. 

GENERALITIES. 

We have given a brief description of those elements 
and compounds which constitute the plant in a chemical 
sense. They are the materials — the stones and timbers, 
so to speak — out of which the vegetable edifice is built. 
It is important, in the next place, to learn how these 
building materials are put together, what positions they 
occupy, what purposes they serve, and on what plan 
the edifice is constructed. 

It is impossible for the builder to do his work until he 
has mastered the plans and specifications of the archi- 
tect. So it is hardly possible for the farmer with cer- 
tainty to contribute in any great, especially in any new, 
degree, to the upbuilding of the plant, unless he is 
acquainted with the mode of its structure and the ele- 
ments that form it. It is the happy province of science 
to add to the vague and general information which the 
observation and experience of generations have taught, 
a more definite and particular knowledge, — a knowledge 
acquired by study purposely and carefully directed to 
special ends. 

An acquaintance with the parts and structure of the 
plant is indispensable for understanding the mode by 
which it derives its food from external sources, while the 
16 241 



242 HOW CROPS GROW. 

ingenious methods of propagation practiced in fruit- and 
flower-culture are only intelligible by the help of this 
knowledge. 

Organism of the Plant. — We have at the outset 
spoken of organic matter, of organs and organization. 
It is in the world of life that these terms have their fit- 
test application. The vegetable and animal consist of 
numerous parts, differing greatly from each other, but 
each essential to the whole. The root, stem, leaf, flower 
and seed are each instruments or organs whose co-oper- 
ation is needful to the perfection of the plant. The 
plant (or animal) being thus an assemblage of organs, is 
called an Organism; it is an Organized or Organic 
Structure. The atmosphere, the waters, the rocks and 
soils of the earth, do not possess distinct co-operating 
parts ; they are Inorganic matter. 

In inorganic nature, chemical affinity rules over the 
transformations of matter. A plant or animal that is 
dead, under ordinary circumstances, soon loses its form 
and characters ; it is gradually consumed, and, at the ex- 
pense of atmospheric oxygen, is virtually burned up to 
air and ashes. 

In the organic world a something, which we call 
Vitality, resists and overcomes or modifies the affinities 
of oxygen, and insures the existence of a continuous and 
perpetual succession of living forms. 

An Organism or Organized Structure is characterized 
and distinguished from inorganic matter by two par- 
ticulars : 

1. It builds up and increases its own mass by appro- 
priating external matter. It absorbs and assimilates 
food. It grows by the enlargement of all its parts. 

2. It reproduces itself. It develops from a germ, and 
in turn gives origin to new germs. 

Ultimate and Complex Organs. — In our account 
of the Structure of the Plant we shall first consider the 



ELEMENTS. OF ORGANIZED STRUCTURE. 243 

elements of that structure — the Cells — which cannot be 
divided or wounded without extinguishing their life, 
and by whose expansion or multiplication all growth 
takes place. Then will follow an account of the com- 
plex parts of the plant — its Organs — which are built up 
by the juxtaposition of numerous cells. Of these we 
have one class, viz., the Roots, Stems and Leaves, whose 
office is to sustain and nourish the Individual Plant. 
These may be distinguished as the Vegetative Organs. 
The other class, comprising the Flower and Fruit, are 
not essential to the existence of the individual, but their 
function is to maintain the Eace. They are the Repro- 
ductive Organs. 

CHAPTER II. 
PRIMARY ELEMENTS OF ORGANIZED STRUCTURE. 

THE VEGETABLE CELL. 

One of the most interesting discoveries that the micro- 
scope has revealed, is that all organized matter originates 
in the form of minute vesicles or cells. If we examine 
by the microscope a seed or an egg, we find nothing but 
a cell-structure — a mass of rounded or many-sided bags 
lying closely together, and more or less filled with solid 
or liquid matters. From these cells, then, comes the 
frame or structure of the plant or of the animal. In the 
process of maturing, the original vesicles are vastly mul- 
tiplied and often greatly modified in shape and appear- 
ance, to suit various purposes ; but still it is always easy, 
especially in the plant, to find cells of the same essential 
characters as those occurring in the seed. 



244 HOW CROPS GROW* 

Cellular Plants. — In the simpler forms or lower 
orders * of vegetation, we find plants which, throughout 
all the stages of their life, consist entirely of similar 
cells, and indeed many are known which are but a single 
cell. The phenomenon of red snow, frequently observed 
in Alpine and Arctic regions, is due to a microscopic 
one-celled plant which propagates with great rapidity, 
and gives its color to the surface of the snow. In the 
chemist's laboratory it is often observed that in the clear- 
est solutions of salts, like the sulphates of sodium and 
magnesium, a flocculent mold, sometimes red, some- 
times green, most often white, is formed, which, under 
the microscope, is seen to be a vegetation consisting of 
single cells. Brewers' yeast, Fig. 27, is nothing more 
than a mass of one or few-celled plants. 

In sea-weeds, mushrooms, the molds that grow on 
damp walls, or upon bread, cheese, etc., and in the 
blights which infest many of the farmer's crops, we have 
examples of plants formed exclusively of cells. 




Fig. 27. Fig. 28. 

All the plants of higher orders we find likewise to 
consist chiefly of globular or angular cells. All the 
growing parts especially, as the tips of the roots, the 
leaves, flowers and fruit, are, for the most part, aggrega- 
tions of such minute vesicles. 

If we examine the pulp of fruits, as that of a ripe 

*Viz. : the Cn/ptogams, including Molds and Mushrooms (Fungi), 
Mosses, Ferns, Sea-Weeds (Algce) and Bacteria {Schizomycetes). 



ELEMENTS OF ORGANIZED STRUCTURE. 245 

apple or tomato, we are able, by means of a low magni- 
fier, to distinguish the cells of which it almost entirely 
consists. Fig. 28 represents a bit of the flesh of a ripe 
pippin, magnified 50 diameters. The cells mostly cohere 
together, but readily admit of separation. 

Structure of the Cell. — By the aid of the micro- 
scope it is possible to learn something with regard to the 
internal structure of the cell itself. Fig. 29 exhibits the 
appearance of a cell from the flesh of the Artichoke 
(Helianthus), magnified 230 diameters ; externally the 
membrane, or wall of the cell, is seen in section. This 
membrane is filled and distended by a 
transparent liquid, the sap or free water 
of vegetation. Within the cell is ob- 
-& served a round body, b, which is called 
the nucleus, and upon this is seen a 
smaller nucleolus, c. Lining the inte- 
rior of the cell-membrane and connected 
with the nucleus, is a yellowish, turbid, 
semi- fluid substance of mucilaginous 
consistence, a, which is designated the protoplasm, or 
formative layer. This, when more highly magnified, is 
found to contain a vast number of excessively minute 
granules. 

By the aid of chemistry the microscopist is able to dis- 
sect these cells, which are hardly perceptible to the 
unassisted eye, and ascertain to a good degree how they 
are constituted. On moistening them with solution of 
iodine, and afterward with sulphuric acid, the outer 
membrane — the cell- wall — shortly becomes of a fine blue 
color. It is accordingly cellulose, the only vegetable 
substance yet known which is made blue by iodine after, 
and only after, the action of sulphuric acid. At the 
same- time we observe that the interior, half-liquid, pro- 
toplasm, coagulates and shrinks together, — separates, 
therefore, from the cell-wall, and, including with it the 




246 HOW CROPS GROW. 

nucleus and the smaller granules, lies in the center of 
the cell like a collapsed bladder. It also assumes a deep 
yellow or brown color. If we moisten one of these cells 
with nitric acid, the cell-wall is not affected, but the 
liquid penetrates it, coagulates the inner membrane, and 
colors it yellow. In the same way this membrane is 
tinged violet-blue by hydrochloric acid. These reactions 
leave no room to doubt that the slimy inner lining of the 
cell or protoplasm contains abundance of albuminoids. 
The protoplasm is not miscible with water and main- 
tains itself distinct from the cell-sap. In young cells it 
is constantly in motion, the granules suspended in it cir- 
culating as in a liquid current. 

If we examine the cells of any other plant we find 
almost invariably the same structure as above described, 
provided the cells are young, i. e., belong to growing 
parts. In some cases isolated cells consist only of proto- 
plasm and nucleus, being destitute of cell-walls during 
a portion or the whole of their existence. 

In studying many of the maturer parts of plants, viz., 
such as have ceased to enlarge, as the full-sized leaf, the 
perfectly formed wood, etc., we find the cells do not cor- 
respond to the description just given. In external shape, 
thickness, and appearance of the cell-wall, and especially 
in the character of the contents, there is indefinite va- 
riety. But this is the result of change in the original 
cells, which, so far as our observations extend, are always, 
at first, formed closely on the pattern that has been de- 
scribed. 

Vegetable Tissue. — It does not, however, usually 
happen that the individual cells of the higher orders of 
plants admit of being obtained separately. They are 
attached together more or less firmly by their outer sur- 
faces, so as to form a coherent mass of cells — a tissue, as 
it is termed. In the accompanying cut, Fig. 30, is shown 
a highly-magnified view of a portion of a very thin slice 



ELEMENTS OF ORGANIZED STRUCTURE. 



247 



across a young cabbage-stalk. It exhibits the outline of 
the irregular empty cells, the walls of which are, for the 
most part, externally united and appear as one, a. At 
the points indicated by h, air-filled cavities between the 
cells are seen, called intercellular spaces. A slice across 
the potato-tuber (see Fig, 52, p. 300) has a similar ap- 
pearance, except that the cells are filled with starch, and 

it would be scarcely pos- 
sible to dissect them apart; 
but when a potato is boiled 
the starch -grains swell, 
and the cells, in conse- 
quence, separate from each 
other, a practical result of 
which is to make the po- 
tato mealy. A thin slice 
of vegetable ivory (the seed 
of Phytelephas macro- 
Fig. 30. car pa) under the micro- 

scope, dry or moistened with water, presents no evident 
trace of cell-structure ; however, upon soaking in sul- 
phuric acid, the mass softens and swells, and the indi- 
vidual cells are revealed, their surfaces separating in 
six-sided outlines. 

Form of Cells. — In the soft, succulent parts of 
plants, the cells lie loosely together, often with consider- 
able intercellular spaces, and have mostly a rounded out- 
line. In denser tissues, the cells are crowded together 
in the least possible space, and hence often appear six- 
sided when seen in cross-section, or twelve-sided if viewed 
entire. A piece of honey comb is an excellent illustra- 
tion of the appearance of many forms of vegetable cell- 
tissue. 

The pulp of an orange is the most evident example of 
cell-tissue. The individual cells of the ripe orange may 
be easily separated from each other. Being mature and 




248 



HOW CHOPS GROW. 



incapable of further growth, they possess neither proto- 
plasm nor nucleus, but are rilled with a sap or juice con- 
taining citric acid, sugar and albuminoids. 

In the pith of the rush, star-shaped cells are found. 
In common mold the cells are long and 
'thread-like. In the so-called frog-spittle 
(algce) they are cylindrical and attached 
end to end. In the bark of many trees, 
in the stems and leaves of grasses, they 
are square or rectangular. 

Cotton-fiber, flax, and hemp consist of 
long and slender cells, Fig. 31. Wood is 
mostly made up of elongated cells, tapered 
at the ends and adhering together by 
their sides. See also Fig. 49, c, h, p. 292. 

Each cotton-fiber is a single cell which forms an 
external appendage to the seed-vessel of the cotton 
'plant. When it has lost its sap and become air-dry, 
its sides collapse and it resembles a twisted strap. 
A, in Fig. 31, exhibits a portion of a cotton-fiber 
highly magnified. The flax-fiber, from the inner 
bark of the flax-stem, b, Fig. 31, is a tube of thicker 
walls and smaller bore than the cotton-fiber, and 
hence is more durable than cotton. It is very flexi- 
ble, and even when crushed or bent short retains much of its original 
tenacity. Hemp-fiber closely resembles flax-fiber in appearance. 

Thickening of the Cell- Membrane. —The growth of the cell, which, 
when young, has a very delicate outer 
membrane, often results in the thick- 
ening of its walls by the interior dep- 
osition of cellulose and woody mat- 
ters. This thickening may take place 
regularly and uniformly, or interrupt- 
edly. The flax-fiber, b, Fig. 31, is an ex- 
ample of nearly uniform thickening. 
The irregular deposition of cellulose is 
shown in Fig. 32, which exhibits a sec- 
tion from tjie seeds (cotyledons) of the 
common nasturtium ( Tropceolum 
magus). The original membrane is coated interiorly with several dis- 
tinct and successively-formed linings, which are not continuous, but 
are irregularly developed. Seen in section, the thickening has a waved 
outline, and, at points, the original cell-membrane is bare. Were these 
cells viewed entire, we should see at these points, on the exterior of 
the cell, dots or circles appearing like orifices, but being simply the 




Fig. 31. 




Fig. 32. 



ELEMENTS OF ORGANIZED STRUCTURE. 249 

unthickened portions of the cell-wall. The cells in fig. 32 exhibit each 
a central nucleus surrounded by grains of aleurone. 

Cell Contents. — Besides the protoplasm and nucleus, 
the cell usually contains a variety of bodies, which have 
been, indeed, noticed already as ingredients of the plant, 
but which may be here recapitulated. Many cells are 
altogether empty, and consist of nothing but the cell- 
wall. Such are found in the bark or epidermis of most 
plants, and often in the pith, and although they remain 
connected with the actually living parts, they have no 
longer any proper life in themselves. 

All living or active cells are distended with liquid. 
This consists of water, which holds in solution gum, dex- 
trin, inulin, the sugars, albuminoids, organic acids, and 
other vegetable principles, together with various salts, 
both of organic and mineral acids, and constitutes the 
sap of the plant. In oil-plants, droplets of oil occupy 
certain cells, Fig. 17, p. 83; while in numerous kinds of 
vegetation colored and milky juices are found in certain 
spaces or channels between the cells. 

The water of the cell comes from the soil, or in some 
cases from the air. The matters, which are dissolved in 
the sap of the plant, together with the semi-solid proto- 
plasm, undergo transformations resulting in the produc- 
tion of various solid substances. By observing the sev- 
eral parts of a plant at the successive stages of its devel- 
opment, under the microscope, we are able to trace 
within the cells the formation and growth of starch- 
grains, of granular or crystalline bodies consisting chiefly 
of albuminoids, and of the various matters which give 
color to leaves and flowers. 

The circumstances under which a cell develops deter- 
mine the character of its contents. The outer cells of 
the potato-tuber are incrusted with corky matter, the 
inner ones are for the most part filled with starch. 

In oats, wheat, and other cereals, we find, just within 



250 HOW CHOPS GROW. 

the skin or epidermis of the grain, a few layers of cells 
that contain scarcely anything but albuminoids, with a 
little fat ; while the interior cells are chiefly filled with 
starch. Fig. 18, p. 110. 

Transformations in Cell Contents — The same 
cell may exhibit a great variety of aspect and contents at 
different periods of growth. This is especially to be ■ 
observed in the seed while developing on the mother 
plant. Hartig has traced these changes in numerous 
plants under the microscope. According to this ob- 
server, the cell-contents of the seed (cotyledons) of the 
common nasturtium (Tropceolum majus) run through 
the following metamorphoses. Up to a certain stage in 
its development the interior of the cells are nearly devoid 
of recognizable solid matters, other than the nucleus and 
the adhering protoplasm. Shortly, as the growth of the 
seed advances, green grains of chlorophyll make their 
appearance upon the nucleus, completely covering it 
from view. At a later stage, these grains, which have 
enlarged and multiplied, are seen to have mostly become 
detached from the nucleus, and lie near to and in contact 
with the cell- wall. Again, in a short time the grains 
lose their green color and assume, both as regards appear- 
ance and deportment with iodine, all the characters of 
starch. Subsequently, as the seed hardens and becomes 
firmer in its tissues, the microscope shows that the 
starch-grains, which were situated near the cell-wall, 
have vanished, while the cell-wall itself has thickened 
inwardly — the starch having been converted into cellu- 
lose or bodies of similar properties. Again, later, the nu- 
cleus, about which, in the meantime, more starch-grains 
have been formed, undergoes a change and disappears ; 
then the starch -grains, some of which have enlarged while 
others have vanished, are found to be imbedded in a pasty 
matter, which has the reactions of an albuminoid. From 
this time on, the starch-grains are gradually converted 



ELEMENTS OF ORGANIZED STRUCTURE. 



251 



from their surfaces inwardly into smaller grains of aleu- 
rone, which, finally, when the seed is mature, completely 
occupy the cells. 

In the sprouting of the seed similar changes occur, but 
in reversed order. The nucleus reappears, the aleurone 
dissolves, and even the cellulose * stratified upon the inte- 
rior of the cell (Fig. 32) wastes away and is converted into 
soluble food (sugar ?) for the seedling plant. 




Fig. 33. 
The Dimensions of Vegetable Cells are very vari- 
ous. A creeping marine plant is known — the Caulerpa 
prolifera (Fig. 33) — which consists of a single cell, though 
it is often a foot in length, and is branched with what 
have the appearance of leaves and roots. The pulp of 

* Or more probably metarabin, paragalactin, xylin, or the like insol- 
uble substances, which as yet have been but imperfectly distinguished 
from cellulose in the thickened cell-walls. 



252 



HOW CROPS GROW. 



the orange consists of cells which are one-quarter of an 
inch or more in diameter. The fiber of cotton is a single 
cell, commonly from one to two inches long. In most 
cases, however, the cells of plants are so small as to re- 
quire a powerful microscope to distinguish them, — are, 
in fact, no more than T ^^ to ^^ of an inch in diame- 
ter. The spores of Fungi are still smaller. The germs 
of many bacteria are so minute as to be undiscoyerable 
by the highest powers of the microscope. 

Growth. — The growth of a plant is nothing more 
than the aggregate result of the enlargement and multi- 
plication of the cells which compose it. In most cases 
the cells attain their full size in a short time. The con- 
tinuous growth of plants depends, then, chiefly on the 
constant and rapid formation of new cells. 

Cell-multiplication. — The young and active cell 





Fig 34. 



Fis:. 35. 



always contains a nucleus (Fig. 34, b). Such a cell may 
produce a new cell by division. In this process the nu. 
cleus, from which all cell-growth appears to originate, is 
observed to resolve itself into two parts, then the proto- 
plasm, a, begins to contract or infold across the cell in a 
line corresponding with the division of the nucleus, until 
the opposite infolded edges meet, — like the skin of a sau- 
sage where a string is tightly tied around it, — thus sepa- 
rating the two nuclei and inclosing each within its new 
ceil, which is completed by a further external growth of 
cellulose. 



ELEMENTS OF ORGANIZED STRUCTURE. 253 

In one-celled plants, like yeast (Fig. 35), the new cells 
thus formed, bud out from the side of the parent-cell, 
and before they obtain full size become entirely detached 
from it, or, as in higher plants, the new cells remain ad- 
hering to the old, forming a tissue. 

In free cell-formation nuclei are observed to develop in 
the protoplasm of a parent cell, which enlarge, surround 
themselves with their own protoplasm and cell-membrane, 
and by the resorption or death of the parent cell become 
independent. 

The rapidity with which the vegetable cells may mul- 
tiply and grow is illustrated by many familiar facts. 
The most striking cases of quick growth are met with in 
the mushroom family. Many will recollect having seen, 
on the morning of a June day, huge purr-balls, some as 
large as a peck measure, on the surface of a moist 
meadow, where the day before nothing of the kind was 
noticed. In such sudden growth it has been estimated 
that the cells are produced at the rate of three or four 
hundred millions per hour. 

Permeability of Cells to Liquids. — Although the 
highest magnifying power that can be brought to bear 
upon the membranes of the vegetable cell fails to reveal 
any apertures in them, — they being, so far as the best- 
assisted vision is concerned, completely continuous and 
imperforate, — they are nevertheless readily permeable to 
liquids. This fact may be shown by placing a delicate 
slice from a potato tuber, immersed in water, under the 
microscope, and then bringing a drop of solution of 
iodine in contact with it. Instantly this reagent pene- 
trates the walls of the unbroken cells without perceptibly 
affecting their appearance, and, being absorbed by the 
starch-grains, at once colors them intensely purplish- 
blue. The particles of which the cell-walls and their 
contents are composed must be separated from each 
other by distances greater than the diameter of the par- 



254 HOW CROPS GROW. 

tides of water or of other liquid matters which thus per- 
meate the cells. 



2. 



THE VEGETABLE TISSUES. 

As already stated, the cells of the higher kinds of 
plants are united together more or less firmly, and thus 
constitute what are known as Vegetable Tissues. Of 
these, a large number have been distinguished by vege- 
table anatomists, the distinctions being based either on 
peculiarities of form or of function. For our purposes 
it will be necessary to define but a few varieties, viz.: 
Cellular Tissue, Wood-Tissue, Bast-Tissue and Vas- 
cular Tissue. 

Cellular Tissue, or Parenchyma, is the simplest of 
all, being a mere aggregation of globular or -polyhedral 
cells whose walls are in close adhesion, and whose juices 
commingle more or less in virtue of this connection. 
Cellular tissue is the groundwork of all vegetable struc- 
ture, being the only form of tissue in the simpler kinds 
of plants, and that out of which all the other tissues are 
developed. 

Prosenchyma is a name applied to all tissues composed 
of elongated cells, like those of wood and bast. Paren- 
chyma and prosenchyma insensibly shade into each 
other. 

Wood-Tissue, in its simplest form, consists of 
cells that are several or many times as long as they arc 
broad, and that taper at each end to a point. These 
spindle-shaped cells cohere firmly together by their sides, 
and "break joints" by overlapping each other, in this 
way forming the tough fibers of wood. Wood-cells are 
often more or less thickened in their walls by depositions 
•of cellulose and other matters, according to their age 



VEGETATIVE ORGANS OF PLANTS. 255 

and position, and are sometimes dotted and perforated, 
as will be explained hereafter — Fig. 53, p. 301. 

Bast-Tissue is made up of long and slender cells, 
similar to those of wood-tissue, but commonly more del- 
icate and flexible. The name is derived from the occur- 
rence of this tissue in the bast, or inner bark. Linen, 
hemp, and most textile materials of vegetable origin, 
cotton excepted, consist of bast-fibers. Bast-cells occupy 
a place in rind, corresponding to that held by wood- 
cells in the interior of the stem — Fig. 49, p. 293. 

Vascular Tissue is the term applied to those un- 
branched Tubes and Ducts which are found in all the 
higher orders of plants, interpenetrating the cellular 
tissue. There are several varieties of ducts, viz. , dotted 
ducts, ringed or annular ducts, and spiral ducts, of 
which illustrations will be given when the minute struc- 
ture of the stem comes under notice— Fig. 49, p. 293. 

The formation of vascular tissue takes place by a sim- 
ple alteration in cellular tissue. A longitudinal series of 
adhering cells represents a tube, save that the bore is 
obstructed with numerous transverse partitions. By the 
removal or perforation of these partitions a tube is devel- 
oped. This removal or perforation actually takes place 
in the living plant by a process of absorption. 



CHAPTER III. 
THE VEGETATIVE ORGANS OF PLANTS. 

THE ROOT. 

The roots of plants, with few exceptions, from the 
first moment of their development, grow downward. . In 
general, they require a moist medium. They will form 
in water or in moist cotton, and in many cases originate 
from branches, or even leaves, when these parts of the 
plant are buried in the earth or immersed in water. It 
cannot be assumed that they seek to avoid the light, 
because they may attain a full development without 
being kept in darkness. The action of light upon them, 
however, appears to be unfavorable to their functions. 

The Growth of Roots occurs mostly by- lengthen- 
ing, and very little or very slowly by increase of thick- 
ness. The lengthening is chiefly manifested toward the 
outer extremities of the roots, as was neatly demonstrated 
by Wigand, who divided the young root of a sprouted 
pea into four equal parts by ink-marks. After three 
days, the first two divisions next the seed had scarcely 
lengthened at all, while the third was double, and the 
fourth eight times its previous length. Ohlerts made 
precisely similar observations on the roots of various 
kinds of plants. The growth is confined to a space of 
about one-sixth of an inch from the tip. (Linnea, 1837, 
pp. 609-631.) This peculiarity adapts the roots to 
extend through the soil in all directions, and to occupy 
256 



VEGETATIVE ORGANS OF PLANTS. 



257 



its smallest pores, or rifts. It is likewise the reason that 
a root, which has been cut off in transplanting or other- 
wise, never afterwards extends in length. 

Although the older parts of the roots of trees and of 
the so-called root-crops acquire a considerable diameter, 
the roots by which a plant feeds are usually thread-like 
and often exceedingly slender. 

Spongioles. — The tips of the rootlets have been 
termed spongioles, or spongelets, from the idea that 
their texture adapts them especially to collect food for 
the plant, and that the absorption of matters from the 
soil goes on exclusively through them. In this sense, 
spongioles do not exist. The real living apex of the 
root is not, in fact, the outmost extremity, but is situ- 
ated a little within that point. 

Root- Cap. — The extreme end of the root usually con- 
sists of cells that have become loosened and in part 

detached from the proper cell-tis- 
sue of the root, which, therefore, 
shortly perish, and serve merely 
as an elastic cushion or cap to 
protect the true termination or 
living point of the root in its act 
of penetrating the soil. Fig. 36 
represents a magnified section of 
part of a barley root, showing the 
loose cells which slough off from 
the tip. These cells are filled 
with air instead of sap. 

A striking illustration of the 
root-cap is furnished by the air- 
roots of the so-called Screw Pine 
(Pandanus odoratissimus), exhibited in natural dimen- 
sions, in Fig. 37. These air-roots issue from the stem 
above the ground, and, growing downwards, enter the 
soil, and become roots in the ordinary sense. 
17 




Fig. 36. 



258 



HOW CROPS GROW. 



When fresh, the diameter of the root is quite^ uni- 
form, but the parts above the root-cap shrink on 'dry- 
ing, while the root-cap itself retains 
nearly its original dimensions; and 
thus reveals its different structure. 

Distinction between Root and 
Stem. — Not all the subterranean 
parts of the plant are roots in a 
proper sense, although commonly 
spoken of as such. The tubers of 
the potato and artichoke, and the 
fleshy horizontal parts of the sweet- 
flag and pepper-root, are merely 
underground stems, of which many 
varieties exist. 

These and all other stems are 
easily distinguished from true roots 
by the imbricated buds, of which 
indications may usually be found on 
their surfaces, e. g., the eyes of the 
potato-tuber. The side or second- 
ary roots are indeed marked in their 
earliest stages by a protuberance on 
the primary root, but these have noth- 
ing in common with the structure of 
true buds. The onion-bulb is itself 
a fleshy bud, as will be noticed subse- 
quently. The true roots of the onion are the fibers 
which issue from the base of the bulb. The roots of 
many plants exhibit no buds upon their surface, and are 
incapable of developing them under any conditions. 
Roots of other plants, such as the plum, apple, and pop- 
lar, may produce buds when cut off from the parent 
plant during the growing season. The roots of the 
former perish if deprived of connection with the stem 
and leaves. The latter may strike out new stems and 




37. 



VEGETATIVE ORGANS OF PLANTS. 259 

leaves for themselves. Plants like the plum are, there- 
fore, cajmble of propagation by root-cuttings, i. e., by 
placing pieces of their roots in warm and moist earth. 

Tap-roots. — All plants whose seeds divide into two 
seed-leaves or Cotyledons, and whose stems increase 
externally by addition of new rings of growth — the 
Dicotyledonous plants, or Exogens — have, at first, a single 
descending axis, the tap-root, which penetrates vertically 
into the ground. From this central tap-root lateral 
roots branch out more or less regularly, and these lateral 
roots subdivide again and again. In many cases, espec- 
ially at first, the lateral roots issue from the tap-root 
with great order and regularity, as much as is seen in 
the branches of the stem of a fir-tree or of a young grape- 
vine. In older plants, this order is lost, because the 
soil opposes mechanical hindrances to regular develop- 
ment. In many cases the tap-root grows to a great 
length, and forms the most striking feature of the indi- 
cation of the plant. In others it enters the ground but 
a little way, or is surpassed in extent by its side branches. 
The tap-root is conspicuous in the Canada thistle, dock 
(Rumex), and in seedling fruit trees. The upper por- 
tion of the tap-root of the beet, turnip, carrot, and rad- 
ish expands under cultivation, and becomes a fleshy, 
nutritive mass, in which lies the value of these plants 
for agriculture. The lateral roots of other plants, as of 
the dahlia and sweet potato, swell out at their extremi- 
ties to tubers. 

Crown Roots. — Monocotyledonous plants, or Endo- 
gens, i. e. , plants whose embryos have only one seed- 
leaf, or Cotyledon, and whose stems .do not increase by 
external additions, such as the cereals, grasses, lilies, 
palms, etc., have no single descending axis or tap-root, 
but produce crown roots, i. e., a number of roots issue 
at once from the base of the stem. This is strikingly 
seen in the onion and hyacinth, as well as in maize. 



260 HOW CROPS GROW. 

Rootlets. — This term we apply to the slender roots, 
but a fevv inches long, which are formed last in the 
order of growth, and correspond to the larger roots as 
twigs correspond to the branches of the stem. 

The Offices of the Root are threefold : 

1. To fix the plant in the earth and maintain it in an 
erect position. 

2. To absorb nutriment from the soil for the growth 
of the entire plant, and, 

3. In case of many plants, especially of those whose 
terms of life extend through several or many years, to 
serve as a store-house for the future use of the plant. 

1. The Firmness with which a Plant is fixed in 
the Ground depends upon the nature of its roots. It 
is easy to lift an onion from the soil ; a carrot requires 
much more force, while a dock may resist the full 
strength of a powerful man. A small beech or seedling 
apple tree, which has a tap-root, withstands the force of 
a wind that would prostrate a maize-plant or a poplar, 
which has only side roots. In the nursery it is the cus- 
tom to cut off the tap-root of apple, peach, and other 
trees, when very young, in order that they may be readily 
and safely transplanted as occasion shall require. The 
depth and character of the soil, however, to a certain 
degree influence the extent of the roots and the tenacity 
of their hold. The roots of maize, which in a rich 
and tenacious earth extend but two or three feet, have 
been traced to a length of ten or even fifteen feet in 
a light, sandy soil. The roots of clover, and especially 
those of alfalfa, extend very deeply into the soil, and the 
latter acquire in some cases a length of 30 feet. The 
roots of the ash have been known as much as 95 feet 
long. {Jour. Roy. Ag. Soc, VI, p. 342.) 

2. Root-absorption. — The Office of Absorbing 
Plant Food from the Soil is one of the utmost impor- 
tance, and one for which the root is most wisely adapted 
by the following particulars, viz. : 



VEGETATIVE ORGANS OF PLANTS. 261 

a. The Delicacy of its Structure, especially that of the 
newer portions, the cells of which are very soft and ab- 
sorbent, as may be readily shown by immersing a .young 
seedling bean in solution of indigo, when the roots 
shortly acquire a blue color from imbibing the liquid, 
while the stem is for a considerable time unaltered. 

It is a common but erroneous idea that absorption 
from the soil can only take place through the ends of the 
roots — through the so-called spongioles. On the con- 
trary, the extreme tips of the rootlets cannot take up liq- 
uids at all. (Ohlerts, loc. cit., see p. 270.) All other 
parts of the roots, which are still young and delicate in 
surface-texture, are constantly active in the work of im- 
bibing nutriment from the soil. 

In most perennial plants, indeed, the larger branches 
of the roots become after a time coated with a corky or 
otherwise nearly impervious cuticle, and the function of 
absorption is then transferred to the rootlets. This is 
demonstrated by placing the old, brown-colored roots of 
a plant in water, but keeping the delicate and unindu- 
rated extremities above the liquid. Thus situated, the 
plant withers nearly as soon as if its root- surface were all 
exposed to the air. 

I. Its Rapid Extension in Length, and the vast Sur- 
face which it puts in contact with the soil, further adapts 
the root to the work of collecting food. The length of 
roots in a direct line from the point of their origin is 
not, indeed, a criterion by which to judge of the effi- 
ciency wtferewith the plant to which they belong is nour- 
ished ; for two plants may be equally flourishing— be 
equally fed by their roots— when these organs, in one 
case, reach but one foot, and in the other extend two feet 
from the stem to which they are attached. In one case, 
the roots would be fewer and longer; in the other, 
shorter and more numerous. Their aggregate length, 
or, more correctly, the aggregate absorbing surface, 
would be nearly the same in both. 



262 HOW CROPS GROW. 

The Medium in which Roots Grow has a great influ- 
ence on their extension. When they are situated in con- 
centrated solutions, or "in a very fertile soil, they are 
short, and numerously branched. Where their food is 
sparse, they are attenuated, and bear a comparatively 
small number of rootlets. Illustrations of the former 
condition are often seen ; moist bones and masses of 
manure are not infrequently found, completely covered 
and penetrated by a fleece of stout roots. On the other 
hand, the roots which grow in poor, dry soils are very 
long and slender. 

Nobba has described some experiments which com- 
pletely establish the point under notice. ( Vs. St., IV, 
p. 212.) He allowed maize to grow in a poor clay soil, 
contained in glass cylinders, each vessel having in it a 
quantity of a fertilizing mixture disposed in some pecu- 
liar manner for the purpose of observing its influence on 
the roots. When the plants had been nearly four months 
in growth, the vessels were placed in water until the earth 
was softened, so that by gentle agitation it could be com- 
pletely removed from the roots. The latter, on being 
suspended in a glass vessel of water, assumed nearly the 
position they had occupied in the soil, and it was ob- 
served that, where the fertilizer had been thoroughly 
mixed with the soil, the roots uniformly occupied its 
entire mass. Where the fertilizer had been placed in a 
horizontal layer at the depth of about one inch, the roots 
at that depth formed a mat of the finest fibers. Where 
the fertilizer was situated in a horizontal layer at half the 
depth of the vessel, just there the root system was sphe- 
roidally expanded. In the cylinders where the fertilizer 
formed a vertical layer on the interior walls, the external 
roots were developed in numberless ramifications, while 
the interior roots were comparatively unbranched. In 
pots, where the fertilizer was disposed as a central vertical 
core, the inner roots were far more greatly developed 



VEGETATIVE ORGANS OF PLANTS. 263 

than the outer ones. Finally, in a vessel where the fer- 
tilizer was placed in a horizontal layer at the bottom, 
the roots extended through the soil, as attenuated and 
slightly branched fibers, until they came in contact with 
the lower stratum, where they greatly increased and ram- 
ified. In all cases, the principal development of the 
roots occurred in the immediate vicinity of the material 
which could furnish them with nutriment. 

It has often been observed that a plant whose aerial 
branches are symmetrically disposed about its stem, has 
the larger share of its roots on one side, and again we find 
roots which are thick with rootlets on one side and 
nearly devoid of them on the other. 

Apparent Search for Food.— It would almost appear, 
on superficial consideration, that roots are endowed with 
a kind of intelligent instinct, for they seem to go in 
search of nutriment. 

The roots of a plant make their first issue independ- 
ently of the nutritive matters that may exist in their 
neighborhood. They are organized and put forth from 
the^plant itself, no matter how fertile or sterile the me- 
dium that surrounds them. When they attain a certain 
development, they are ready to exercise their office of 
collecting food. If food be at hand, they absorb it, and, 
together with the entire plant, are nourished by it— they 
grow in consequence. The more abundant the food, the 
better they are nourished, and the more they multiply. 
The plant sends out rootlets in all directions ; those 
which come in contact with food, live, enlarge, and ram- 
ify ; those which find no nourishment, remain undevel- 
oped or perish. 

The Quantity of Roots actually belonging to any Plant 
is usually far greater than can be estimated by roughly 
lifting them from the soil. To extricate the roots of 
wheat or clover, for example, from the earth, completely, 
is a matter of extreme difficulty. Schubart was the first 



264 HOW CROPS GROW. 

to make satisfactory observations on the roots of several 
important crops, growing in the field. He separated 
them from the soil by the following expedient : An exca- 
vation was made in the field to the depth of 6 feet, and 
a stream of water was directed against the vertical wall 
of soil until it was washed away, so that the roots of the 
plants growing in it were laid bare. The roots thus ex- 
posed in a field of rye, in one of beans, and in a bed of 
garden peas, presented the appearance of a mat or felt of 
white fibers, to a depth of about 4 feet from the surface 
of the ground. The roots of winter wheat he observed 
as deep as 7 feet, in a light subsoil, forty-seven days after 
sowing. The depth of the roots of winter wheat, winter 
rye, and winter colza, as well as of clover, was 3 to 4 feet. 
The roots of clover, one year old, were 3^- feet long, those 
of two-year -old clover but four inches longer. The quan- 
tity of roots in per cent of the entire plant in the dry 
state was found to be as follows. (Chem. Acker smann, 
I, p. 193.) 

Winter wheat— examined last of April 40% 

« « " " » May 22" 

" rye " ' " "April 34" 

Peas examined four weeks after sowing 44 " 

" " at the time of blossom 24" 

Hellriegel has likewise studied the radication of barley 
and oats (Hoff, Jahresberlcht, 1864, p. 106.) He raised 
plants in large glass pots, and separated their roots from 
the soil by careful washing with water. He observed 
that directly from the base of the stem 20 to 30 roots 
branch-off sideways and downward. These roots, at 
their point of issue, have a diameter of ^ of an inch, 
but a little lower the diameter diminishes to about T fa of 
an inch. Eetaining this diameter, they pass downward, 
dividing and branching to a certain depth. From these 
main roots branch out innumerable side roots, which 
branch again, and so on, filling every crevice and pore of 
the soil. 



VEGETATIVE ORGANS OF PLANTS. 



265 



To ascertain the total length of root, Hellriegel weighed 
and ascertained the length of selected average portions. 
Weighing then the entire root-system, he calculated the 
entire length. He estimated the length of the roots of a 
vigorous barley plant at 128 feet, that of an oat plant at 
150 feet.* He found that a small bulk of good fine soil 
sufficed for this development ; -£$ cubic foot (4 — |— 4 -f- 2§ 
in.) answered for a barley plant, ^ cubic foot for an 
oat plant, in these experiments. 

Hellriegel observed also that the quality of the soil in- 
fluenced the development. In rich, porous, garden-soil, 
a barley plant produced 128 feet of 
roots, but in a coarse-grained, com- 
pacter soil, a similar plant had but 80 
feet of roots. 

Boot Hairs. — The real absorbent 
surface of roots is, in most cases, not 
to be appreciated without microscopic 
aid. The roots of the onion and of 
many other bulbs, i. e., the fibers which 
issue from the base of the bulbs, are per- 
fectly smooth and un branched through- 
out their entire length. Other agricul- 
tural plants have roots which are not 
only visibly branched, but whose finest 
fibers are more or less thickly covered 
with minute hairs, scarcely perceptible 
to the unassisted eye. These root-hairs 
consist always of tubular elongations of 
the external root-cells, and through 
them the actual root-surface exposed 
to the soil becomes something almost 
Fig. 38. incalculable. The accompanying fig- 

ures illustrate the appearance of root-hairs. 

Fig. 38 represents a young mustard seedling. A is 

* Rhenish, 34= 35 English feet. 




266 HOW CROPS GROW. 

the plant, as carefully lifted from the sand in which it 
grew, and B the same plant, freed from adhering soil 
by agitating in water. The entire root, save the tip, 
is thickly beset with hairs. In Fig. 39 a minute portion 
of a barley-root is shown highly magnified. The hairs 
are seen to be slender tubes that proceed from, and form 
part of, the outer cells of the root. 

The older roots lose their hairs, and suffer a thicken.- 
ing of the outermost layer of cells. These dense-walled 
and nearly impervious cells cohere together and consti- 
tute a rind, which is not found in the young and active 
roots. 

As to the development of the 
root-hairs, they are more abund- 
ant in poor than in good soils, 
and appear to be most numer- 
ously produced from roots which 
have otherwise a dense and un- 
absorbent surface. The roots of 
those plants which are destitute 
of hairs are commonly of con'sid-^i 
erable thickness and remain 
white and of delicate texture, 
preserving their absorbent power Flg * 39, 

throughout the whole time that the plant feeds from the 
soil, as is the case with the onion. 

The Silver Fir (Abies Picea) has no root-hairs, but its 
rootlets are covered w T ith a very delicate cuticle highly 
favorable to absorption. The want of root-hairs is fur- 
ther compensated by the great number of rootlets which 
are formed, and which, perishing mostly before they be- 
come superficially indurated, are continually replaced by 
new ones during the growing season. (Schacht, Der 
Baum, p. 165.) 

Contact of Foots with the Soil. — The root-hairs, as 
they extend into the soil, are naturally brought into close 




VEGETATIVE ORGANS OF PLANTS. 



267 




Fig. 40. 



Fig. 4L 



268 



HOW CROPS GROW. 



contact with its particles. This contact is much more 
intimate than has been usually supposed. If we care- 
fully lift a young wheat-plant from dry earth, we notice 
that each rootlet is coated with an envelope of soil. This 
adheres with considerable tenacity, so that gentle shak- 
ing fails to displace it, and if it be mostly removed by 




Fig. 42. 

vigorous agitation or washing, the root-hairs are either 
found to be broken, or in many places inseparably at- 
tached to the particles of earth. 

Fig. 40 exhibits the appearance of a young wheat- 



VEGETATIVE ORGANS OF PLANTS. 



269 



plant as lifted from the soil and pretty strongly shaken. 
S, the seed ; b, the blade ; e, roots covered with hairs 
and enveloped in soil. Only the growing tips of the 
roots, w, which have not put forth hairs, come out clean 
of soil. Fig. 41 represents the roots of a wheat-plant 
one month older than those of the previous figure. In 
this instance not only the root-tips are naked as before, 
but the older parts of the primary roots, e, and of the 
secondary roots, n. no longer retain the particles of soil ; 
the hairs upon them being, in fact, dead and decom- 
posed. The newer parts of the root alone are clothed 
with active hairs, and to these the soil is firmly attached 
as before. The next illustration, Fig. 42, exhibits the 

appearance of root-hairs with ad- 
hering particles of earth, w 7 hen mag- 
nified 800 diameters : A, root-hairs 
of wheat-seedling, like Fig. 40; B, 
of oat- plant, both from loamy soil. 
Here is plainly seen the intimate 
attachment of the soil and rcot- 
hairs. The latter, in forcing their 
way against considerable pressure, 
often expand around, and partially 
envelop, the particles of earth. 
(Sachs's Exp. Phys. d. Pflanzen.) 
Imbibition of water by the root. — 
The force with which active roots 
imbibe the water of the soil is 
sufficient to force the liquid upward 
into the stem and to exert a continu- 
al pressure on all parts of the j)lant. 
When the stem of a plant in vigor- 
ous growth is cut off near the root, 
and a pressure-gauge is attached to 
it, as in Fig. 43, w r e have the means of observing and 
measuring the force with which the roots absorb water. 




Fig. 43. 



270 HOW CHOPS GKOW. 

The pressure-gauge contains a quantity of mercury in 
the middle .reservoir, b, and the tube, c. It is attached 
to the stem of the plant, p, by a stout india-rubber 
pipe, g.* For accurate measurements, the space a and 
b should be filled with water. Thus arranged, it is found 
that water will enter a through the stem, and the mer- 
cury will rise in the tube, e, until its pressure becomes 
sufficient to balarce the absorptive power of the roots. 
Stephen Hales, who first experimented in this manner 
(1721) found in one instance that the pressure exerted 
on a gauge, attached in springtime to the stump of a 
grape-vine, supported a column of mercury 32J inches 
high, which is equal to a column of water of 36^ feet. 
Hofmeister obtained on other plants, rooted in pots, the 
following results : 

Bean {Phaseolus midtiflorus) 6 inches of mercury. 

Nettle 14 " » 

Vine 29 " " 

The seat of absorption Dutrochet demonstrated to be 
the surface of the young and active roots. At least, he 
found that absorption was exerted with as much force 
when the gauge was applied to near the lower extremity 
of a root as when attached in the vicinity of the stem. 
In fact, when other conditions are alike, the column of 
liquid sustained by the roots of a plant is greater the less 
the length of stem that remains attached to them. The 
stem thus resists the rise of liquid in the plant. 

While the seat of absorptive power in the root lies 
near the extremities, it appears from the experiments of 
Ohlerts that the extremities themselves are incapable of 
imbibing water. In trials with young pea, flax, lupine 
and horseradish plants with unbranched roots, he found 
that they withered speedily when the tips of the roots 
were immersed for about one-fourth of an inch in water, 



*For experimenting on small plants, a simple lube of glass may be 
adjusted to the stump vertically by help of a rubber connector. 



. VEGETATIVE ORGANS OF PLANTS. 271 

the remaining parts being in moist air. Ohlerts like- 
wise proved that these plants flourish when only the 
middle part of their roots is immersed in water. Keep- 
ing the root-tips, the so-called spongioles, in the air, or 
cutting them away altogether, was without apparent 
effect on the freshness and vigor of the plants. The 
absorbing surface would thus appear to be confined to 
those portions of the root upon which the development 
of root-hairs is noticed. 

The absorbent force is manifested by the active root- 
lets, and most vigorously when these are in the state of 
most rapid development. For this reason we find, in 
case of the vine, for example, that during the autumn, 
when the plant is entering upon a period of repose from 
growth, the absorbent power is trifling. Sometimes 
water is absorbed at the roots so forcibly as not only to 
distend the plant to the utmost, but to cause the sap of 
the plant to exude in drops upon the foliage. This may 
be noticed upon newly-sprouted maize, or other cereal 
plants, where the water escapes from the leaves at their 
extreme tips, especially when the germination has pro- 
ceeded under the most favorable conditions for rapid 
development. 

The bleeding of the vine, when severed in the spring- 
time, the abundant flow of sap from the sugar-maple 
and the water-elm, are striking illustrations of this 
imbibition of water from the soil by the roots. These 
examples are, indeed, exceptional in degree, but not in 
kind. Hofmeister has shown that the bleeding of a sev- 
ered stump is a general fact, and occurs with all plants 
when the roots are active, when the soil can supply them 
abundantly with water, and when the tissues above the 
absorbent parts are full of this liquid. When it is other- 
wise, water may be absorbed from the gauge into the 
stem and large roots, until the conditions of activity are 
renewed. 



272 HOW CEOPS GROW. 

Of the external circumstances that affect this absorp- 
tive power, heat and light would appear to be influential. 
By observing a gauge attached to the stump of a plant 
during a clear summer day, it will be usually noticed 
that the mercury begins to rise in the morning as the 
sun warms the soil, and continues to ascend for a num- 
ber of hours, but falls again as the sun declines. Sachs 
found in some of his experiments that, in case of potted 
tobacco and squash plants, absorption was nearly or 
entirely suppressed by cooling the roots to 41° F., but 
was at once renewed by plunging the pots into warm 
water. 

The external supplies of water, — in case a plant is 
stationed in the soil, the degree of moisture contained in 
this medium, — obviously must influence any manifesta- 
tion of the imbibing force. But full investigation shows 
that this regular daily fluctuation is a habit of the plant 
which is independent of small changes of temperature 
and even of considerable variation in the amount of mois- 
ture of the soil. 

The rate of absorption is subject to changes depend- 
ent on causes not well understood. Sachs observed 
that the amount of liquid which issued from potato 
stalks cut off just above the ground underwent great 
and continual variation from hour to hour (during rainy 
weather) when the soil was saturated with w r ater and 
when the thermometer indicated a constant temperature. 
Hofmeister states that the formation of new roots and 
buds on the stump is accompanied by a sinking of the 
water in the pressure-gauge. 

Absorption of Nutriment from the Soil. — The food of 
the plant, so far as it is derived from the soil, enters it 
in a state of solution, and is absorbed with the water 
which is taken up by the rootlets. The absorption of 
the matters dissolved in water is in some degree inde- 
pendent of the absorption of the water itself, the plant 



VEGETATIVE ORGANS OF PLANTS. 2T3 

having apparently, to a certain extent, a selective power. 
See p. 401. 

3. The Root as a Magazine. — In Fleshy Tap- 
Roots, like those of the carrot, beet, and turnip, the 
absorption of nutriment from the soil takes place princi- 
pally, if not entirely, by means of the slender rootlets 
which proceed abundantly from all their surface, and 
especially from their lower extremities, while the older 
fleshy part serves as a magazine in which large quantities 
of carbhydrates, etc., are stored up during the first year's 
growth of these biennial plants, to supply the wants of 
the flowers and seed which are developed the second year. 
When one of these roots, put into the ground for a sec- 
ond year, has produced seed, it is found to be quite 
exhausted of the nutritive matters which it previously 
contained in so large quantity. 

Root Tubers, like those of the dahlia and sweet potato, 
are fleshy enlargements of lateral or secondary roots 
filled with reserve material, from which buds and new 
stems may develop. Small tubers {Tubercles) are fre- 
quently formed on the roots of the garden bean 
(Phaseohis). 

In cultivation, the farmer not only greatly increases 
the size of these roots and the stores of organic nutritive 
materials they contain, but, by removing them from the 
ground in autumn, he employs to feed himself and his 
cattle the substances that nature primarily designed to 
nourish the growth of flowers and seeds during another 
summer. 

Soil-Roots ; Water-Roots ; Air-Roots. — We mav 
distinguish, according to the medium in which they are 
formed and grow, three kinds of roots, viz. : soil-roots, 
water -roots, and air-roots. 

Most agricultural plants, and indeed by far the greater 
number of all plants found in temperate climates, have 
roots adapted especially to the soil, and which perish by 
18 



#74 HOW CROPS GROW. 

short exposure to dry air, or rot, if long immersed in 
water. Many aquatic plants, on the other hand, speed- 
ily die when their roots are removed from water, or from 
earth saturated with water, and exposed to the atmos- 
phere or stationed in earth of the usual dryness. 

Air-roots are not common except among tropical plants 
or under tropical conditions of heat and moisture. In- 
dian corn, when thickly planted and of rank growth, 
often throws out roots from the lower joints of the stem, 
which extend through the air several inches before they 
reach the soil. The same may be observed of many com- 
mon plants, as the oat, grape, potato, and buckwheat, 
when they long remain in hot, moist air. The Banyan- 
tree of India sends out from its branches, vertically, 
pendants several yards long which penetrate the earth 
and there become soil-roots. 

On the other hand, various tropical plants, especially 
Orchids, emit roots which hang free in the air and never 
reach the earth. In the humid forest ravines of Madeira 
and Teneriffe, the Lauras Canariensis, a large tree, 
sends out from its stem^during the autumn rains, a pro- 
fusion of fleshy air-roots, which cover the trunk with 
their interlacing branches and grow to an inch in thick- 
ness. The following summer they dry away and fall to 
the ground, to be replaced by new ones in the ensuing 
autumn. (Schacht, Der Baum, p. 172.) 

A plant, known to botanists as the Zamia spiralis, not 
only throws out air-roots, c c, Fig. 44, from the crown of 
the main soil-root, but the side rootlets, "b, after extend- 
ing some distance horizontally in the soil, send, from the 
same point, roots downward and upward, the latter of 
which, d, pass into and remain permanently in the air. 
a is the stem of the plant. (Schacht, A?iatomie der 
Geivachse, Bd. II, p. 151.) 

The formation of air-roots may be very easily observed 
by placing water to the depth of half an inch in a tall 



VEGETATIVE ORGANS OF PLANTS. 



275 



vial, inserting a sprig of the common greenhouse-plant 
Tradesccmiia zebrina, so that the cut end of the stem 
shall stand in the water, and finally corking the vial air- 
tight. The plant, which is very tenacious of life, and 
usually grows well in spite of all neglect, is not checked 
in its vegetative development by the treatment just de- 
scribed, but immediately begins to adapt itself to its 
new circumstances. In a few days, if the temperature 
be 70° or thereabout, air-roots will be seen to issue from 
the joints of the stem. These are fringed with a profu- 
sion of delicate hairs, and rapidly extend to a length of 
from one to two inches. The lower ones, if they chance 




Fig. 44. 
to penetrate the water, become discolored and decay ; the 
others, however, remain for a long time fresh, and of a 
white color. 

Some plants have roots which are equally able to exist 
and perform their functions, whether in the soil or sub- 



276 HOW CROPS GROW. 

merged in water. Many forms of vegetation found in 
our swamps and marshes are of this kind. Of agricul- 
tural plants, rice is an example in point. Eice will grow 
in a soil of ordinary character, in respect of moisture, as 
the upland cotton -soils, or even the pine-barrens of the 
Carolinas. It flourishes admirably in the tide-swamps of 
the coast, where the land is laid under water for weeks 
at a time during its growth, and it succeeds equally well 
in fields which are flowed from the time of planting to 
that of harvesting. (Eussell, North America, its Agri- 
culture and Climate, p. 176.) The willow and alder, 
trees which grow on thq margins of streams, send a part 
of their roots into soil that is constantly saturated with 
water, or into the water itself ; while others occupy the 
merely moist or even dry earth. 

Plants that customarily confine their growth to the 
soil occasionally throw out roots as if in search of water, 
and sometimes choke up drain-pipes or even wells by the 
profusion of water-roots which they emit. At Welbeck, 
England, a drain was completely stopped by roots of 
horse-radish plants at a depth of 7 feet. At Thornsby 
Park, a drain 16 feet deep was stopped entirely by the 
roots of gorse, growing at a distance of 6 feet from the 
drain. (Jour. Roy. Ag. Soc, I, p. 364.) In New 
Haven, Connecticut, certain wells are so obstructed by the 
aquatic roots of the elm trees as to require cleaning out 
every two or three years. This aquatic tendency has 
been repeatedly observed in the poplar, cypress, laurel, 
turnip, mangel-wurzel, and various grasses. 

Henrici surmised that the roots which most cultivated 
plants send down deep into the soil, even when the latter 
•is by no means porous or inviting, are designed especially 
to bring up water from the subsoil for the use of the 
plant. He devised the following experiment, which ap- 
pears to prove the truth of this view. On the 13th of 
May, 1862, a young raspberry plant, having but two 



VEGETATIVE ORGANS OF PLANTS. 2T7 

leaves, was transplanted into a large glass funnel filled 
with garden soil, the throat of the funnel being closed 
with a paper filter. The funnel was supported in the 
mouth of a large glass jar, and its neck reached nearly to 
the bottom of the latter, where it just dipped into a 
quantity of water. The soil in the fuunel was at first 
kept moderately moist by occasional waterings. The 
plant remained fresh and slowly grew, putting forth new 
leaves. After the lapse of several weeks, four strong 
roots penetrated the filter and extended down the empty 
funnel-neck, through which they emerged, on the 21st 
of June, and thenceforward spread rapidly in the water 
of the jar. From this time on, the soil was not watered 
any more, but care was taken to maintain the supply in 
the jar. The plant continued to develop slowly ; its 
leaves, however, did not acquire a vivid green color, but 
remained pale and yellowish ; they did not wither until 
the usual time, late in autumn. The roots continued to 
grow, and filled the water more and more. Near the 
end of December the plant had seven or eight leaves, and 
a height of eight inches. The water- roots were vigorous, 
very long, and beset with numerous fibrils and buds. In 
the funnel tube the roots made a perfect tissue of fibers. 
In the dry earth of the funnel they were less extensively 
developed, yet exhibited some juicy buds. The stem 
and the young axillary leaf-buds were also full of sap. 
The water-roots being cut away, the plant was put into 
garden soil and placed in a conservatory, where it grew 
vigorously, and in May bore tw T o offshoots. (Hennelerg's 
Jour, far Landwirtlischaft, 1863, p. 280.) This growth 
towards water must be accounted for on the principles 
asserted in the paragraph, Apparent Search for Food 
(p. 263). 

The seeds of many ordinary land plants — of plants, 
indeed, that customarily grow in a dry soil, such as the 
bean, squash, maize, etc. — will readily germinate in 



278 HOW CROPS GROW. 

moist cotton or sawdust, and if, when fairly sprouted, 
the young plants have their roots suspended in water, 
taking care that the seed and stem are kept above the 
liquid, they will continue to grow, and with due supplies 
of nutriment will run through all the customary stages 
of development, produce abundant foliage, blossoms, and 
perfect seeds, without a moment's contact of their roots 
with soil. (See Water Culture, p. 181.) 

In plants thus growing with their roots in a liquid 
medium, after they have formed several large leaves, be 
carefully transplanted to the soil, they wilt and perish, 
unless frequently watered ; whereas similar plants, started 
in the soil, may be transplanted without suffering in the 
slightest degree, though the soil be of the usual dryness, 
and receive no water. 

The water-bred seedlings, if abundantly watered as 
often as the foliage wilts, recover themselves after a time, 
and thenceforward continue to grow without the need of 
watering. 

It might appear that the first-formed water-roots are 
incapable of feeding the plant from a dry soil, and hence 
the soil must be at first profusely watered ; after a time, 
however, new roots are thrown out, which are adapted to 
the altered situation of the plant, and then the growth 
proceeds in the usual manner. 

The reverse experiment would seem to confirm this 
view. If a seedling that has grown for a short time only 
in the soil, so that its roots are but twice or thrice 
branched, have these immersed in water, the roots 
already formed mostly or entirely perish in a short time. 
They indeed absorb water, and the plant is sustained by 
them, but immediately new roots grow from the crown 
with great rapidity, and take the place of the original 
roots, which become disorganized and useless. It is, 
however, only the young and active rootlets, and those 
covered with hairs, which thus refuse to live in water. 



VEGETATIVE ORGANS OF PLANTS. 279 

The older parts of the roots, whieh are destitute of fibrils 
and which have nearly ceased to be active in the work of 
absorption, are not affected by the change of circum- 
stance. These facts, which are due to the researches of 
Dr. Sachs ( Vs. St., II, p. 13), would naturally lead to 
the conclusion that the absorbent surface of the root un- 
dergoes some structural change, or produces new roots 
with modified characters, in order to adapt itself to the 
medium in which it is placed. It would appear that 
when this adaptation proceeds rapidly the plant is not 
permanently retarded in its growth by a gradual change 
in the character of the medium which surrounds its 
roots, as may happen in case of rice and marsh-plants, 
when the saturated soil in which they may be situated at 
one time is slowly dried. Sudden changes of medium 
about the roots of plants slow to adapt themselves would 
be fatal to their existence. ■ 

Nobbe has, however, carefully compared the roots of 
buckwheat, as developed in the soil, with those emitted 
in water, without being able to observe any structural 
differences. The facts above detailed admit of partial, if 
not complete, explanation, without recourse to the suppo- 
sition that soil- and water-roots are essentially diverse in 
nature. When a plant which is rooted in the soil is 
taken up so that the fibrils are not broken or injured, 
and set into water, it does not, suffer any hindrance in 
growth, as Sachs found by his later experiments. (Ex- 
perimental Phy&iologie, p. 177.) Ordinarily, the suspen- 
sion of growth and decay of fibrils and rootlets is due, 
doubtless, to the mechanical injury they suffer in remov- 
ing from the soil. Again, when a plant that has been 
reared in water is planted in earth, similar injury occurs 
in packing the soil about the roots, and moreover the 
fibrils cannot be brought into that close contact with the 
soil which is necessary for them to supply the foliage 
with water ; hence the plant wilts, and may easily perish 



280 HOW CROPS GBOW. 

unless profusely watered or shielded from evaporation. 

The air-roots of Orchids, which never reach the soil, 
have a peculiar spongy texture and take up the water 
which exists as vapor in the air, as shown by the experi- 
ments of linger, Chatin, and Sachs. Duchartre's inves- 
tigations led him to deny their absorptive power. (Ele- 
ments de Botanique, p. 216.) In his experiments made 
on entire plants, the air-roots failed to make good the 
loss by evaporation from the other parts of the plant. 

It is evident from common observation that moisture 
is the condition that chiefly determines root-develop- 
ment. Not only do all seeds sprout and send forth roots 
when provided with abundant moisture at suitable tem- 
peratures, but generally older roots and stems, and 
fleshy leaves, or cuttings from these, will produce new 
rootlets when properly circumstanced as regards moisture, 
whether that moisture be supplied by aid of a covering 
of damp soil, wet sand or paper, by stationing in humid 
air, or by immersion in water itself. 

Root-Excretions. — It was formerly supposed that 
the roots of plants perform a function of excretion, the 
reverse of absorption — that plants, like animals, reject 
matters which are no longer of use in their organism, 
and that the rejected matters are poisonous to the kind 
of vegetation from which they originated. De Candolle, 
an eminent French botanist, who first advanced this doc- 
trine, founded it upon the observation that certain plants 
exude drops of liquid from their roots w T hen these are 
placed in dry sand, and that odors exhale from the roots 
of other plants. Numerous experiments have been in- 
stituted at various times for the purpose of testing this 
question. Noteworthy are those of Dr. Alfred Gyde 
(Trans. Highland and Agr. Soc, 1845-47, pp. 273-92). 
This experimenter planted a variety of agricultural plants, 
viz., wheat, barley, oats, rye, beans, peas, vetches, cab- 
bage, mustard, and turnips, in pots filled either with 



VEGETATIVE ORGANS OF PLANTS. 281 

garden soil, sand, moss, or charcoal, and after they had 
attained considerable growth, removed the earth, etc., 
from their roots by washing with water, using care not 
to injure or wound them, and then immersed the roots 
in vessels of pure water. The plants were allowed to re- 
main in these circumstances, their roots being kept in 
darkness, but their foliage exposed to light, from three 
to seventeen days. In most cases they continued appa- 
rently in a good state of health. At the expiration of 
the time of experiment, the water which had been in 
contact with the roots was evaporated, and was found to 
leave a very minute amount of yellowish or brown mat- 
ter, a portion of which was of organic and the remainder 
of mineral origin. Dr. Gyde concluded that plants do 
throw off organic and inorganic excretions similar in 
composition to their sap ; but that the quantity is ex- 
ceedingly small, and is not injurious to the plants which 
furnish them. 

In the light of newer investigations touching the 
structure of roots and their adaptation to the medium 
which happens to invest them, we may well doubt 
whether agricultural plants in the healthy state excrete 
any solid or liquid matters whatever from their roots. 
The familiar excretion of gum, resin, and sugar* from 
the stems of trees appears to result from wounds or dis- 
ease, and the matters which in the experiments of Gyde 
and others were observed to be communicated by the 
roots of plants to pure water probably came either from 
the continual pushing off of the tips of the rootlets by 
the interior growing point— a process always naturally 
accompanying the growth of roots— or from the disor- 
ganization of the absorbent root-hairs. 

Under certain circumstances, small quantities of sol- 
uble salts or free acids may indeed diffuse out of the 

California!' 6 wounded bark of the sugar-pine (ttnus Lambertiana) of 



282 HOW CROPS GROW, 

root-cells into the water of the soil. This is, however, 
no physiological action, but a purely physical process. 

Vitality of Roots. — It appears that in case of most 
plants the roots cannot long continue their vitality if 
their connection with the leaves be interrupted, unless, 
indeed, they be kept at a winter temperature. Hence 
weeds may be effectually destroyed by cutting down 
their tops ; although, in many cases, the process must 
be several times repeated before the result is attained. 

The roots of our root-crops, properly so-called, viz., 
beets, turnips, carrots, and parsnips, when harvested in 
autumn, contain the elements of a second year's growth 
of stem, etc., in the form of a bud at the crown of the 
root. If the crown be cut away from the root, the latter 
cannot vegetate, while the growth of the crown itself is 
not thereby prevented. 

As regards internal structure, the root closely resem- 
bles the stem, and what is stated of the latter, on subse- 
quent pages, applies in all essential points to the former. 



2. 



THE STEM. 

Shortly after the protrusion of the rootlet from a ger- 
minating seed, the Stem makes its appearance. It has, 
in general, an upward direction, which in many plants 
is permanent, while in others it shortly falls to the 
ground and grows thereafter horizontally. 

All plants of the higher orders have stems, though in 
many instances they do not appear above ground, but 
extend beneath the surface of the soil, and are usually 
considered to be roots. 

While the root, save in exceptional cases, does not 
develop other organs, it is the special function of the 
stem to bear the leaves, flowers, and seed of the plant, 



VEGETATIVE ORGANS OF PLANTS. 



283 



and even in certain tribes of vegetation, like the cacti, 
which have no leaves, to perform the offices of these 
organs. In general, the functions of the stem are sub- 
ordinate to those of the organs which it bears — the leaves 
and flowers. It is the support of these organs, and, it 
would appear, only extends in length or thickness with 
the purpose of sustaining them mechanically or provid- 
ing them with nutriment. 

Buds. — In the seed the stem exists in a rudimentary 
state, associated with undeveloped leaves, forming a bud. 
The stem always proceeds at first from a bud, during all 
its growth is terminated by a bud at every growing point, 
and only ceases to be thus tipped when it fully accom- 
plishes its growth by the production of seed, or dies 
from injury or disease. 

In the leaf -Mid we find a number of embryo leaves 
and leaf-like scales, in close contact and within each 
other, but all at- 
tached at the base 
to a central conical 
axis, Fig. 45. The 
opening of the bud 
consists in the 
lengthening of this 
axis, which is the 
stem, and the con- 
sequent separation 
from each other as 

well as expansion of Fig. 45. 

the leaves. If the 

rudimentary leaves of a bud be represented by a nest of 
flower-pots, the smaller placed within the larger, the 
stem may be signified by a rope of India-rubber passed 
through the holes in the bottom of the pots. The 
growth of the stem may now be shown by stretching the 
rope, whereby the pots are brought away from each 





284: HOW CROPS GROW. 

other, and the whole combination is made to assume the 
character of a fully-developed stem, bearing its leaves at 
regular intervals ; with these important differences, that 
the portions of stem nearest the root extend more rap- 
idly than those above them, and the stem has within it 
the material and the mechanism for the continual for- 
mation of new buds, which unfold in successive order. 

In Fig. 45, which represents the two terminal buds of 
a lilac twig, is shown not only the external appearance 
of the buds, which are covered with leaf-like scales, 
imbricated like shingles on a roof ; but, in the section, 
are seen the edges of the undeveloped leaves attached to 
the conical axis. All the leaves and the whole stem of 
a twig of one summer's growth thus exist in the bud, in 
plan and in miniature. Subsequent growth is but the 
development of the plan. 

In the flower-bud the same structure is manifest, save 
that the rudimentary flowers and fruit are enclosed 
within the leaves, and may often be seen plainly on cut- 
ting the bud open. 

Nodes; Internodes. — Nodes are those knots or parts 
of the stem where the leaves are attached. The portions 
of the stem between the nodes are termed internodes. 
It is from the nodes that roots most freely develop when 
stems (layers or cuttings) are surrounded by moist air or 
soil. 

Culms. — The grasses and the common cereal grains 
have single, unbranched stems, termed culms in botani- 
cal language. The leaves of these plants clasp the stem 
entirely at their base, and rest upon a well-defined, thick- 
ened node. 

Branching Stems. — Other agricultural plants besides 
those just mentioned, and all the trees of temperate cli- 
mates, have branching stems. As the principal or main 
stem elongates, so that the leaves arranged upon it sepa- 
rate from each other, we find one or more buds at the 



VEGETATIVE OKGANS OF PLANTS. 285 

point where the base of the leaf or of the leaf-stalk 
unites with the stem. From these axillary buds, in case 
their growth is not checked, side-stems or branches 
issue, which again subdivide in the same manner into 
branchlets. 

In perennial plants, when young, or in their young 
shoots, it is easy to trace the nodes and internodes, or 
the points where the leaves are attached and the inter- 
vening spaces, even for some time after the leaves, which 
only endure for one year, are fallen away. The nodes 
are manifest by the enlargement of the stem, or by the 
scar, covered w T ith corky matter, which marks the spot 
where the leaf-stalk was attached. As the stem grows 
older these indications of its early development are grad- 
ually obliterated. 

In a forest where the trees are thickly crowded, the 
lower branches die away from want of light; the scars 
resulting from their removal, or short stumps of the 
limbs themselves, are covered with a new growth of 
wood, so that the trunk finally appears as if it had always 
been destitute of branches, to a great height. 

When all the buds develop normally and in due pro- 
portion, the plant, thus regularly built up, has a sym- 
metrical appearance, as frequently happens with many 
herbs, and also with some of the cone-bearing trees, 
especially the balsam-fir. 

Latent Buds. — Often, however, many of the buds 
remain undeveloped, either permanently or for a time. 
Many of the side-buds of most of our forest and fruit 
trees fail entirely to grow, wiiile others make no progress 
until the summer succeeding their first appearance. 
When the active buds are destroyed, either by frosts or 
by pinching off, other buds that would else remain 
latent are pushed into growth. In this way trees 
whose young leaves are destroyed by spring frosts cover 
themselves again, after a time, with foliage. In this way, 



28G HOW CROPS GROW. 

too, the gardener molds a straggling, ill-shaped shrub or 
plant into almost any form he chooses ; for, by removing 
branches and buds where they have grown in undue pro- 
portion, he not only checks excess, but also calls forth 
development in the parts before suppressed. Close 
pruning, or breaking the young twigs causes abundant 
development of flower-buds on fruit trees that otherwise 
"run to wood." 

Adventitious or irregular Buds are produced from 
the stems as well as older roots of many plants, when 
they are mechanically injured during the growing season. 
The soft or red maple and the chestnut, when cut down, 
habitually throw out buds and new stems from the 
stump, and the basket-willow is annually polled, or pol- 
larded, to induce the growth of slender shoots from an 
old trunk. 

Elongation of Stems. — While roots extent! chiefly 
at their extremities, we find the stem elongates equally, 
or nearly so, in all its contiguous parts, as is manifest 
from what has already been stated in illustration of its 
development from the bud. 

Besides the upright stem, there are a variety of pros- 
trate and in part subterranean stems, which may be 
briefly noticed. 

Runners and Layers are stems that are sent out hor- 
izontally just above the soil, and, coming in contact with 
the earth, take root, forming new plants, which may 
thenceforward grow independently. The gardener takes 
advantage of these stems to propagate certain plants. 
The strawberry furnishes the most familiar example of 
runners, while many of the young shoots of the currant 
fall to the ground and become layers. The runner is a 
somewhat peculiar stem. It issues horizontally, and 
usually bears but few or no leaves. The layer does not 
differ from an ordinary stem, except by the circum- 
stance, often accidental, of becoming prostrate. Many 



VEGETATIVE ORGAN'S OF PLANTS. 287 

plants which usually send out no layers are nevertheless 
artificially layered by bending their stems or branches to 
the ground, or by attaching to them a ball or pot of 
earth. The striking out of roots from the layer is in 
many cases facilitated by cutting half through, twisting, 
or otherwise wounding the stem at the point where it is 
buried in the soil. 

The tillering of wheat and other cereals, and of many 
grasses, is the spreading of the plant by layers. The first 
stems that appear from these plants ascend vertically, 
but, subsequently, other steins issue, whose growth is, 
for a time, nearly horizontal. They thus come in con- 
tact with the soil, and emit roots from their lower joints. 
From these again grow new stems and new roots in rapid 
succession, so that a stool produced from a single kernel 
of winter wheat, having perfect freedom of growth, has 
been known to carry 50 or 60 grain -bearing culms. 
(Hallet, Jour. .Roy. Soc. of Eng., 22, p. 372.) 

Suckers. — When branches arise from the stem below 
the surface of the soil, so that they are partly subter- 
ranean and partly aerial, as in the Eose and Raspberry, 
they are termed Suckers. These leafy shoots put out 
roots from their buried nodes, and may be separated 
artificially and used for propagating the plant. 

Subterranean Stems. — Of these there are three 
forms. They are usually taken to be roots, from the 
fact of existing below T the surface of the soil. This cir- 
cumstance is, however, quite accidental. The pods of 
the peanut (Arachis hypogcea) ripen beneath the 
ground — the flower-stems lengthening and penetrating 
the earth as soon as the blossom falls ; but these stems 
are not by any means to b3 confounded with roots. 

Root-stocks, or Rhizomes. — True roots are desti- 
tute of leaves. This fact easily distinguishes them from 
the rhizome, which is a stem that extends below the sur- 
face of the ground. At the nodes of these root-stocks, 



288 



HOW CROPS GROW. 



as they are appropriately named, scales or rudimentary 
leaves are seen, and thence roots proper are emitted. In 
the axils of the scales may be traced the buds from which 
aerial and fruit-bearing stems proceed. Examples of 
the root-stock are very common. Among them we mav 
mention the blood-root and pepper-root as abundant in 
the woods of the Northern and Middle States, various 
mints, asparagus, and the quack-grass (Agropyram* 
repens) represented in Fig. 46, which infests so many 
farms. Each node of the root-stock, being usually sup- 
plied with roots, and having latent buds, is ready to 
become an independent growth the moment it is detached 




Fisr. 46. 



from its parent plant. In this way quack-grass becomes 
especially troublesome, for the more the fields where it 
has obtained a footing are tilled the more does it com- 
monly spread and multiply; only oft-repeated harrow- 
ing in a season of prolonged dryness suffices for its 
extirpation. 

Corms are enlargements of the base of the stem, bear- 
ing leaf-buds either at the summit or side, and may be 
regarded as much-shortened rhizomes, with only a few 
slightly-developed intern odes. Externally they resemble 
bulbs. The garden crocus furnishes an example. 

Tubers of many plants are fleshy enlargements of the 



* Formerly Triticum. 



VEGETATIVE ORGANS OF PLANTS. 289 

extremities of subterranean stems. Their eyes are the 
points where the buds exist, usually three together, 
and where minute scales — rudimentary leaves — may be 
observed. The common potato and artichoke (Helian- 
thus tuber osus) are instances of this kind of tubers. 
Tubers serve excellently for propagation. Each eye, or 
bud, may become a new plant. From the quantity of 
starch, etc., accumulated in them, they are of great 
importance as food. The number of tubers produced by 
a potato-plant appears to be increased by planting orig- 
inally at a considerable depth, or by "hilling up" earth 
around the base of the aerial stems during the early 
stages of its growth. 

Bulbs are greatly thickened stems, whose leaves — 
usually having the form of fleshy scales or concentric coats 
— are in close contact with each other, and arise from 
nearly a. common base, the internodes being undeveloped. 
The bulb is, in fact, a permanent bud, usually in part 
or entirely subterranean. . From its apex, the proper 
stem, the foliage, etc., proceed; while from its base 
roots are sent out. The structural identity of the bulb 
with a bud is shown by the fact that the onion, which 
furnishes the commonest example of the bulb, often 
bears bulblets at the top of its stem, in place of flowers. 
In like manner, the axillary buds of the tiger-lily are 
thickened and fleshy, and fall off as bulblets to the 
ground, where they produce new plants. 

Structure of the Stem. — The stem is so compli- 
cated that to discuss it fully would occupy a volume. 
For our immediate purposes it is, how r ever, only neces- 
sary to notice its structural composition very concisely. 

The rudimentary stem, as found in the seed, or the 
new-formed part of the maturer stem at the growing 
points just below the terminal buds, consists of cellular 
tissue, or is an aggregate of rounded and cohering cells, 
which rapidly multiply during the vigorous growth of 
the plant. 19 



290 HOW CROPS GROW. 

In some of the lower orders of vegetation, as in mush- 
rooms and lichens, the stem, if any exist, always pre- 
serves a purely cellular character ; but in all flowering 
plants the original cellular tissue of the stem, as well as 
of the root, is shortly penetrated by vascular tissue, 
consisting of ducts or tubes, which result from the 
obliteration of the horizontal partitions of cell-tissue, 
and by wood-cells, which are many times longer than 
wide, and the walls of which are much thickened by 
internal deposition. 

These ducts and wood-cells, together with some other 
forms of cells, are usually found in close connection, and 
are arranged in bundles, which constitute the fibers of 
the stem. They are always disposed lengthwise in the 
stem and branches. They are found to some extent in 
the softest herbaceous stems, while they constitute a 
large share of the trunks of most shrubs and trees. 
From the toughness which they possess, and the manner 
in which they are woven through the original cellular 
tissue, they give to the stem its solidity and strength. 

Flowering plants may be divided into two great classes, 
in consequence of important and obvious differences in 
the structure of their stems and seeds. These are : 1, 
Monocotyledons, or Endogens ; and 2, Dicotyledons, or Exo- 
gens. As regards their stems, these two classes of plants 
differ in the arrangement of the vascular or woody tissue. 

Endogenous Plants are those whose stems enlarge by 
the formation of new wood in the interior, and not by 
the external growth of concentric layers. The embryos 
in the seeds cf endogenous plants consist of a single piece 
— do not readily split into halves — or, in botanical lan- 
guage, have but one cotyledon; hence are called monoco- 
tyledonous. Indian corn, sugar-cane, sorghum, wheat, 
oats, rye, barley, the onion, asparagus, and all the 
grasses, belong to this tribe of plants. 

If a stalk of maize, asparagus, or bamboo be cut 



VEGETATIVE ORGANS OF PLANTS. 291 

across, the fiber-like bundles of ducts and wood-cells are 
seen disposed somewhat uniformly throughout the sec- 
tion, though less abundantly towards the center. On 
splitting the fresh stalk lengthwise, these vascular bun- 
dies may be torn out like strings. At the nodes, where 
the stem is branched, or where leaf -stalks are attached, 
the vascular bundles likewise divide and form a net-work. 
In a ripe maize-stalk which is exposed to circumstances 
favoring decay, the soft cell-tissue first suffers change 
and often quite disappears, leaving the firmer vascular 
bundles unaltered in form. A portion of the base of 
such a stalk, cut lengthwise, is represented in Fig. 47, 
where the vascular bundles are seen arranged parallel to 
each other in the internodes, and curiously interwoven 
and branched at the nodes, both at those (a and b) from 
which roots issued, or at that (c) which was clasped by 
the base of a leaf. 

The endogenous stem, as represented in the maize- 
stalk, has no well-defined bark that admits of being 




Fig. 47. 

stripped off externally, and no separate central pith of 
soft cell-tissue free from vascular bundles. It, like the 
aerial portions of all flowering plants, is covered with a 
skin, or epidermis, composed usually of one or several 
layers of flattened cells, whose walls are thick, and far 
less penetrable to fluid than the delicate texture of the 
interior cell-tissue. The stem is denser and harder at 
the circumference than towards the center. This is due 
to the fact that the bundles are more numerous and 
older towards the outside of the stem. The newer bun- 
dles, as they continually form at the base of the growing 
terminal bud, pass to the inside of the stem, and af^er- 



29-> 



HOW CROPS GROW. 



wards outwards and downwards, and hence the designa- 
tion endogenous, which in plain English means inside- 
grower. 

In consequence of this inner growth, the stems of 
most woody endogens, as the palms, after a time become 
so indurated externally that all lateral expansion ceases, 
and the stem increases only in height. In some cases, 
the tree dies because its interior is so closely packed with 




Fief. 48. 



bundles that the descent of new ones, and the accom- 
panying vital processes, become impossible. 

In herbaceous endogens the soft stem admits the 
indefinite growth of new vascular tissue. 



VEGETATIVE ORGANS OF PLANTS. 



293 



The stems of the grasses are hollow, except at the 
nodes. Those of the rushes have a central pith free from 
vascular tissue. 

The Minute Structure of the Endogenous Stem 
is exhibited in the accompanying cuts, which represent 
highly magnified sections of a Vascular Bundle or fiber 
from the maize-stalk. As before remarked, the stem is 
composed of a groundwork of delicate cell-tissue, in 
which bundles of vascular-tissue are distributed. Fig. 
48 represents a cross section of one of these bundles, c, 
g, h, as well as of a portion of the surrounding cell -tis- 




Fig. 49. 

sue, a, a. The latter consists of quite large cells, winch 
have between them considerable inter-cellular spaces, i. 
The vascular bundle itself is composed externally of 
narrow, thick-walled cells, of which those nearest the 
exterior of the stem, h, are termed bast -cells, as they 
correspond in character and position to the cells of the 
bast or. inner bark of our common trees; those nearest 
the center of the stem, c, are wood-cells. In the maize 
stem, bast-cells and wood-cells are quite alike, and are 



294 HOW CROPS GROW. • 

distinguished only by their position. In other plants, 
they are often unlike as regards length, thickness, and 
pliability, though still, for the most part, similar in 
form. Among the wood-cells we observe a number of 
ducts, d, e, /, and between these and the bast-cells is a 
delicate and transparent tissue, g, which is the cambium, 
in which all the growth of the bundle goes on until it 
is complete. On either hand is seen a remarkably large 
duct, b, b, while the residue of the bundle is composed 
of long and rather thick-walled wood-cells. 

Fig. 49 represents a section made vertically through 
the bundle from c to h. In this the letters refer to the 
same parts as in the former cut : a, a is the cell-tissue, 
enveloping the vascular bundle ; the cells are observed 
to be much longer than wide, -but are separated from 
each other at the ends as well as sides by an imperforate 
membrane. The wood and bast-cells, c, h, are seen to 
be long, narrow r , thick-walled cells running obliquely to 
a point at either end. The wood-cells of oak, hickory, 
and the toughest woods, as well as the bast-cells of flax 
and hemp, are quite similar in form and appearance. 
The proper ducts of the stem are next in the order of 
our section. Of these there are several varieties, as ring- 
ducts, d;. spiral ducts, e; dotted ducts,/. These are 
continuous tubes produced by the absorption of the 
transverse membranes tiiat once divided them into such 
cells as a, a, and they are thickened internally by ring- 
like, spiral, or punctate depositions of cellulose (see Fig. 
32, p. 248). Wood or bast-cells that consist mainly of 
cellulose are pliant and elastic. It is the deposition of 
other matters (so-called lignin) in their walls which ren- 
ders them stiff and brittle. 

At g, the cambial tissue is observed to consist of del- 
icate cylindrical cells. Among these, partial absorption 
of the separating membrane often occurs, so th,at they 
communicate directly with each other through sieve-like 



VEGETATIVE ORGANS OF PLANTS. 



295 



partitions, and become continuous channels or ducts. 
(Sieve-cells, p. 303.) The cambium is the seat of growth 
by cell-formation. Accordingly, when a vascular bun- 
dle has attained maturity, it no longer possesses a cam- 
bium. 

To complete our view of the vascular bundle, Fig. 50 
represents a vertical section made at right angles to the 
last, cutting two large ducts, b, b; a, a is cell-tissue; 




Fig. 50. 



c, c are bast or wood-cells less thickened by interior 
deposition than those of Fig. 49 ; d is a ring and spiral 
duct ; b, b are large dotted ducts, which exhibit at g, g 
the places where they were once crossed by the double 
membrane composing the ends of two adhering cells, by 
whose absorption and removal an uninterrupted tube 
has been formed. In these large dotted ducts there 
appears to be no direct communication with the sur- 
rounding cells tli rough their sides. The dots or pits 
are simply very thin points in the cell-wall, through 
which sap may soak or diffuse laterally, but not flow. 



296 HOW CHOPS GROW. ' 

When the cells become mature and cease growth, the 
pits often become pores by absorption of the membrane, 
so that the ducts thus enter into direct communication 
with each other. 

Exogenous Plants are those whose stems contin- 
ually enlarge in diameter by the formation of new tissue 
near the outside of the stem. They are outside-fjrowers. 
Their seeds are usually made up of two loosely-united 
parts, or cotyledons, wherefore they are designated 
dicotyledonous. All the forest trees of temperate cli- 
mates, and, among agricultural plants, the bean, pea, 
clover, potato, beet, turnip, flax, etc., are exogens. 

In the exogenous stem the bundles of ducts and fibers 
that appear in the cell-tissue are always formed just 
within the rind. They occur at first separately, as in 
the enclogens, but, instead of being scattered throughout 
the cell- tissue, are disposed in a circle. As they grow, 
they usually close up to a ring or zone of wood, which 
incloses unaltered cell-tissue — the pith. 

As the stem enlarges, new rings of fibers may be 
formed, but always outside the older ones. In hard 
stems of slow growth the rings are close together and 
chiefly consist of very firm wood-cells. In the soft stems 
of herbs the cellular tissue preponderates, and the ducts 
and cells of the vascular zones are delicate. The harden- 
ing of herbaceous stems which takes place as they become 
mature is due to the increase and induration of the 
wood-cells and ducts. 

The circular disposition of the fibers in the exogenous 
stem may be readily seen in a multitude of common 
plants. 

The potato tuber is a form of stem always accessible 
for observation. If a potato be cut across near the stem- 
end with a sharp knife, it is usually easy to identify upon 
the section a ring of vascular-tissue, the general course 
of which is parallel to the circumference of the tuber 



VEGETATIVE ORGANS OF PLANTS. 297 

except where it runs out to the surface in the eyes or 
buds, and in the narrow stem at whose extremity it 
grows. If a slice across a potato be soaked in solution 
of iodine for a few minutes, the vascular ring becomes 
strikingly apparent. In its active cambial cells, albu- 
minoids are abundant, which assume a yellow tinge with 
iodine. The starch of the cell-tissue, on the other hand, 
becomes intensely blue, making the vascular tissue all 
the more evident. 

Since the structure of the root is quite similar to that 
of the stem, a section of tbe common beet as well as one 
of a branch from any tree of temperate latitudes may 
serve to illustrate the concentric arrangement of the vas- 
cular zones when they are multipled in number. 

Pith is the cell-tissue of the center of the stem. In 
young stems it is charged with juices; in older ones it 
often becomes dead and sapless. In many cases, espec- 
ially when growth is active, it becomes broken and nearly 
obliterated, leaving a hollow stem, as in a rank pea-vine, 
or clover-stalk, or in a hollow potato. In the potato 
tuber the pith-cells are occupied throughout with starch, 
although, as the coloration by iodine makes evident, the 
quantity of starch diminishes from the vascular zone 
towards the center of the tuber. 

The Rind, which, at first, consists of mere epidermis, 
or short, thick-walled cells, overlying soft cellular tissue, 
becomes penetrated with cells of unusual length and 
tenacity, which, from their position in the plant, are 
termed bast-cells. These, together with ducts of various 
kinds, constitute the so-called last, which grows chiefly 
upon the interior of the rind, in successive annual layers, 
in close proximity to the wood. With their abundant 
development and with age, the rind becomes lark as it 
occurs on shrubs and trees. The bast-cells give to the 
bark its peculiar toughness, and cause it to come off the 
stem in long and pliant strips. 



298 HOW CEOPS GROW. 

All the vegetable textile materials employed in the man- 
ufacture of cloth and cordage, with the exception of cot- 
ton, as flax, hemp, New Zealand flax, etc., are bast-fibers. 
(Seep. 248.) 

In some plants the annual layers of bast are so sepa- 
rated by cellular tissue that in old stems they may be 
split from one another. Various kinds of matting are 
made by weaving together strips of bast layers, especially 
those of the Linden (Bass-wood or Bast-wood) tree. The 
leather-wood or moose-wood bark, often employed for 
tying flour-hags, lias bast-fibers of extraordinary tenacity. 
The bast of the grape-vine separates from the stem in 
long shreds a year or two after its formation. 

The epidermis of young stems is replaced, after a cer- 
tain age, by the corky layer. This differs much in dif- 
ferent plants. In the Birch it is formed of alternate 
layers of large- and small-celled tissue, and splits and 
curls up. From the Plane-tree it is thrown off period- 
ically in large plates by the expansion of the cellular tis- 
sue underneath. In the Maple, Elm, and Oak, especially 
in the Cork-Oak, it receives annual additions on its 
inner side and does not separate : after a time it conse- 
quently acquires considerable thickness, the growth of 
the stem furrows it with deep rifts, and it gradually 
decays or drops away exteriorly as the newer bark forms 
within. 

Pith Rays. — Those portions of the first-formed cell- 
tissue which were interposed between the young and 
originally ununited wood-fibers remain, and connect the 
pith with the cellular tissue of the bark. They inter- 
rupt the straight course of the bast- cells, producing the 
netted appearance often seen in bast layers, as in the 
Lace-bark. In hard stems they become flattened by 
the pressure of the fibers, and are readily seen in most 
kinds of wood when split lengthwise. They are espe- 
cially conspicuous in the Oak and Maple, and form what 



VEGETATIVE ORGANS OE PLANTS. 



299 




is commonly known as the silver-grain. The botanist 

terms them pith-rays, or medullary 
rays. 

Fig. 51 exhibits a section of 
spruce wood, magnified 200 di- 
ameters. The section is made 
lengthwise of the wood-cells, four 
of which are in part represented, 
and cuts across the pith-rays, 
whose cell-structure and position 
in the wood are seen at m, n. 

Branches have the same struct- 
ure as the stems from which they 
spring. Their tissues traverse 
those of the stem to its center, 
\\ II \ \lll^ wnere they connect with the pith 
1 \iv/\ and its sheath of spiral ducts. 

Cambium of Exogens. — The 
'*& 5L growing part of the exogenous 

stem is between the fully formed wood and the ma- 
ture bark. There is, in fact, no definite limit where 
•wood ceases and bark begins, for they are connected by 
the cambial or formative zone, from which, on the one 
hand, wood-fibers, and on the other, bast-fibers, rapidly 
develop. In the cambium, likewise, the pith-rays which 
connect the inner and outer parts of the stem continue 
their outward growth. 

In spring-time the new cells that form in the cambial 
region are very delicate and easily broken. For this 
reason the rind or bark may be stripped from the wood 
without difficulty. In autumn these cells become thick- 
ened and indurated — become, in fact, full-grown bast and 
wood-cells — so that to peel the bark off smoothly is im- 
possible. 

Minute Structure of Exogenous Stems. — The ac- 
companying figure (52) will serve to convey an idea of 



300 



HOW CROPS GROW. 



the minute structure of the elements of the exogenous 
stem. It exhibits a section lengthwise, through a young 
potato tuber magnified 200 diameters ; a, b is the rind ; 
e the vascular ring ; / the pith. The outer cells of the 
rind are converted into cork. They # have become empty 
of sap and are nearly impervious to air and moisture. 
This corky-layer, a, constitutes the thin coat or skin that 
may be so readily peeled off from a boiled potato. When- 
ever a potato is superficially wounded, even in winter 
time, the exposed part heals over by the formation of 




Fig. 52. 



cork-cells. The cell tissue of the rind consists at its 
center, b, of full-formed cells with delicate membranes 
which contain numerous and large starch grains. On 
either hand, as the rind approaches the corky-layer or 
the vascular ring, the cells are smaller, and contain 
smaller starch grains ; at either side of these are noticed 
cells containing no starch, but having nuclei, c, y. These 
nucleated cells are capable of multiplication, and they 
are situated where the growth of the tuber takes place. 
The rind,* which makes a large part of the flesh of the 
potato, increases in thickness by the formation of new 
cells within and without. Without, where it joins the 
corky skin, the latter likewise grows. Within, contigu- 

* The word rind is here used in its hotanical (not in the ordinary) 
sense, to denote that part of the tuber which corresponds to the rind of 
the stem. 



VEGETATIVE ORGANS OF PLANTS. 



301 



ous to the vascular zone, new ducts are formed. In a 
similar manner, the pith expands by 
formation of new cells, where it joins 
the vascular tissue. The latter consists, 
in our figure, of ring, spiral, and dotted 
ducts, like those already described as j 
occurring in the maize-stalk. The deli- 
cate cambial cells, c, are in the region of 
most active growth. At this point new 
cells rapidly develop, those to the right, 
x in the figure, remaining plain cells and 
becoming loosely filled with starch ; 
S \ ^ // Af\'* tnose t° the left developing new ducts. 
In the slender, overground potato- 
stem, as in all the stems of most agri- 
cultural plants, the same relation of 
parts is to be observed, although the 
vascular and woody tissues often pre- 
ponderate. Wood -cells are especially 
abundant in those stems that need 
strength for the fulfilment of their offices, 
and in them, especially in those of our 
trees, the structure is commonly more 
@ \\ complicated. 

Pitted Wood-Cells of the Coni- 
fers. — In the wood of cone-bearing trees 
=' ' there are no proper ducts, such as have 

been described. The large wood-cells which constitute 
the concentric rings of the wood are constructed in a spe- 
cial manner, being provided laterally with pits, or; accord- 
ing to Schacht, with visible pores, through which the 
fluid contents o£ one cell may easily diffuse (by osmose), 
or even pass directly into those of its neighbors. 

Fig. 53, B represents a portion of an isolated wood-cell 
of the Scotch Fir (Pinus xylvestris) magnified 200 diam- 
eters. Upon it are seen nearly circular disks, x, y, the 



302 



HOW CROPS GROW. 



structure of which, while the cell is young is shown by 
a section through them lengthwise. A exhibits such a 
section through the thickened walls of two contiguous 
and adhering cells, x, in both A and B, shows a cavity 
between the two primary cell-walls ; yu the narrow 
part of the channel, that 



remains while the mem 
brane thickens around it. 
This is seen at y, as a pit 
in each cell-wall, or, as 
Schacht believed, a pore 
or opening from cell to 
cell. In A it appears 
closed because the section 
passes a little to one side 
of the pore. (Schacht.) 

In the next figure (54), 
representing a transverse 
section of the spring wood 
of the same tree magnified 
300 diameters, the struct- 
ure and the gradual form- 
ation of these pore-disks 
is made evident. The sec- 
tion, likewise, gives an in- 
structive illustration o f 
the general character of the 
simplest kind of wood. R 
are the young cells of the 
rind ; C is the cambium, 
where cell-multiplication 




Fig. 54. 



goes on; W is the wood, whose cells are more developed 
the older they are, i. e., the more distant fcom the cam- 
bium, as is seen from their figure and the thickness of 
their walls. At a is shown the disk in its earliest stage , 
b and e exhibit it in a more advanced growth. At a tne 



VEGETATIVE ORGANS OF PLANTS. 303 

disk has become a pore, the primary membrane has been 
absorbed, and a free channel made between the two cells. 
The dotted lines at d lead out laterally to two concentric 
circles, which represent the disk-pore seen flatwise, as in 
Fig. 53. At e the section passes through the new 
annual ring into the autumn wood of the preceding year. 
Sieve-cells, or Sieve-ducts. — The spiral, ring, and 
dotted ducts and pitted wood-cells already noticed, ap- 
pear only in the older parts of the vascular bundles, and, 
although they may be occupied with sap at times when the 
stem is surcharged with water, they are ordinarily filled 
with air alone. The real transmission of the nutritive 
juices of the growing plant, so far as it goes on through 
actual tubes, is now admitted to proceed in an independ- 
ent set of ducts, the so-called sieve-tubes, which are usu- 
ally near to and originate from the cambium. These 
are extremely delicate, elongated cells, whose transverse 
or lateral walls are perforated, sieve-fashion (by absorp- 
tion of the original membrane) so as to establish direct 
communication from one to another, and this occurs 
while they are yet charged with juices and at a time 
when the other ducts are occupied with air alone. These 
sieve-ducts are believed to be the channels through which 
the organic matters that are formed in the foliage mostly 
pass in their downward movement to nourish the stem 
and root. Fig. 55 represents the sieve-cells in the over- 
ground stem of the potato ; A, B, cross-section of parts 
of vascular bundle ; A, exterior part towards rind ; B, 
interior portion next to pith ; a, a, cell-tissue inclosing 
the smaller sieve-cells, A, B, which contain sap turbid 
with minute granules ; b, cambium cells ; c, wood-cells 
(which are absent in the potato tuber) ; d, ducts inter- 
mingled with wood-cells. C represents a section length- 
wise of the sieve-ducts ; and D, more highly magnified, 
exhibits the finely perforated, transverse partitions, 
through which the liquid contents more or less freely 
pass. 



304 



HOW CROPS GROW. 



d 



Milk Ducts. — Besides the ducts already described, 
there is, in many plants, a system of irregularly branched 
channels containing a milky juice {latex) as in the 
sweet potato, dande- j± 

lion, milk-weed, etc. 
These milk- ducts a 
occur in all parts of 
the plants, but most 
abundantly in the 
pith and inner bark 
of stems and in the 
cellular tissue of ^ 
roots. They often so 
completely permeate 
all the organs of the 
plant that the slight- 
est wound breaks 
some of them and 
causes a flow of latex. 
The hitter, like ani-a' 
mal milk, is a watery 
fluid holding in sus- 
pension minute gran- 
ules or drops which 
make it op a q u e. a 
The latex often con- 
tains the organic 
substances peculiar 
to the plant, acquires 
a sticky, viscid char- 
acter, and hardens Fig. 55. 
on exposure to the air. Opium, India-rubber, gutta- 
percha, and various resins are dried latex. Alkaloids 
frequently occur, and ferments like papain (p. 104) are 
probably not uncommon in this secretion. 

Herbaceous Stems. — Annual stems of the exogenous 




VEGETATIVE ORGANS OF PLANTS. 305 

kind, whose growth is entirely arrested by winter, consist 
usually of a single ring of woody tissue with interior 
pith and surrounding bark. Often, however, the zone 
of wood is thin, and possesses but little solidity, while 
the chief part of the stem is made up of cell-tissue, so 
that the stem is herbaceous. 

Woody Stems. — Perennial exogenous stems consist, 
in temperate climates, of a series of rings or zones, cor- 
responding in number with that of the years during 
which their growth has been progressing. The stems of 
our shrubs and trees, especially after the first few years of 
growth, consist, for the most part, of woody tissue, the 
proportion of cell-tissue being very small. 

The annual cessation of growth which occurs at the 
approach of winter is marked by the formation of smaller 
or finer wood-cells, as shown in Fig. 54, e, while the 
vigorous renewal of activity in the cambium at spring- 
time is exhibited by the growth of larger cells, and in 
many kinds of wood in the production of ducts, which, 
as in the oak, are visible to the eye at the interior of the 
annual layers. 

Sap-wood and Heart-wood. — The living processes 
in perennial stems, while proceeding with most force in 
the cambium, are not confined to that locality, but go on 
to a considerable depth in the wood. Except at the 
cambial layer, however, these processes consist not in the 
formation of new cells, nor the, enlargement of those 
once formed — not properly in growth — but in the trans- 
mission of sap and the deposition of organized matter on 
the interior of the wood-cells. In consequence of this 
deposition the inner or heart-wood of many of our forest 
trees becomes much denser in texture and more durable 
for industrial purposes. It then acquires a color differ- 
ent from the outer or sap-wood (alburnum), becomes 
brown in most cases, though it is yellow in the barberry 
and red in the red cedar. 
20 



306 HOW CROPS GROW. 

The final result of the filling up of the cell of the 
heart-wood is to make this part of the stem almost or 
quite impassable to sap, so that the interior wood may be 
removed by decay without disturbing the vigor of the 
tree. 

Passage of Sap through the Stem. — The stem, 
besides supporting the foliage, flowers and fruit, has also 
a most important office in admitting the passage upward 
to these organs of the water and mineral matters which 
enter the plant by the roots. Similarly, it allows the 
downward transfer to the roots of substances gathered 
by the foliage from the atmosphere. To this and other 
topics connected with the ascent and descent of the sap 
we shall hereafter recur. 

The stem constitutes the chief part by weight of many 
plants, especially of forest trees, and serves the most im- 
portant uses in agriculture, as well as in a thousand other 
industries. 

§ 3 - 

LEAVES. 

These most important organs issue from the stem, are 
at first folded curiously together in the bud, and after- 
wards expand so as to present a great amount of surface 
to the air and light. 

The leaf consists of a thin membrane of cell-tissue 
directly connected with the cellular layer of the bark, 
arranged upon a skeleton or net-work of fibers and ducts 
continuous with those of the inner bark and wood. 

In certain plants, as cactuses, there scarcely exist any 
leaves, or, if any occur, they do not differ, except in 
external form, from the stems. Many of these plants^ 
above ground, are in form all stem, while in structure 
and function they are all leaf. 

In the grasses, although the stem and leaf are distin- 




PLATE II. 



explanation. (See p. 213.) 
Water-cultures of Flowering Bean after vegetating 38 days. 

a. In normal solution, seed with cotyledons. 

b. In normal solution, seed without cotyledons. 

c. In potassium-free solution, seed with cotyledons. 

d. In potassium-free solution, seed without cotyledons. 



VEGETATIVE ORGANS OF PLANTS. 307 

guishable in shape, they are but little unlike in other 
external characters. 

In forest trees, we find the most obvious and striking 
differences between the stem and leaves. 

Color of Leaves. — A peculiarity most character- 
istic of the leaves of the higher orders of plants, so long 
as tbey are in vigorous discharge of their proper vegeta- 
tive activities, is the possession of a green color, due to 
the presence of Chlorophyl. (See p. 124.) This color 
is also proper in most cases to the young bark of the 
stem, a fact further indicating the connection between 
these parts, or rather demonstrating their identity of 
origin and function, for it is true, not only in the case 
of the cactuses, but also in that of all other young 
plants, that the green (young) stems perform, to some 
"extent, the same offices as the leaves, the latter being, in 
fact, growths from and extensions of the bark. 

The loss of green color that occurs in autumn, in the 
foliage of our deciduous trees, or on the maturing of the 
plant, as with the cereal grains, is related to the cessa- 
tion of growth and death of the leaf, and results from 
chemical changes in the chlorophyl-pigment. 

Plants naturally destitute of chlorophyl, like Indian 
pipe (Monotropa), Dodder (Cuscuta), Mushrooms, 
Toadstools, and fungi generally, are parasites on living 
or dead organisms, from which they derive their nour- 
ishment. Such plants cannot construct organic sub- 
stances out of inorganic matters, as do the plants having 
chlorophyl. 

When leaves, ordinarily green, are totally excluded 
from light, or develop at a low temperature, they have a 
pale yellow color; on exposure to light and warmth they 
become green. In both cases the Chloropliyl-gramiles 
are formed, but the chlorophyl-pigment appears only in 
the latter. In absence of iron, leaves are white, contain 
no chlorophyl granules, and growth is arrested. 



308 HOW CROPS GROW. 

There are many leafy plants cultivated for ornamental purposes 
with more or less brown, red, yellow, white, or variegated foliage, 
which are by no means destitute of ehlorophyl, as is shown by micro- 
scopic examination, though this substance is associated with other 
coloring matters which mask its green tint. 

Structure of Leaves. — While in shape, size, modes 
of arrangement upon and attachment to the stem, we 
find among leaves no end of diversity, there is great sim- 
plicity in the matter of their internal structure. 

The whole surface of the leaf, on both sides, is cov- 
ered with epidermis, a coating which, in many cases, 
may be readily stripped off the leaf, and consists of thick- 
walled cells, which are, for the most part, devoid of liq- 
uid contents, except when very young. (F, E, Fig. 56.) 

Fig. 56 represents the appearance of a bit of bean-leaf as seen on a 
section from the upper to the lower surface, and highly magnified. 

Below t?he upper epidermis, there often occur one or 
more layers of oblong cells, whose sides are in close con- 
tact, and which are arranged endwise, with reference to 
the flat of the leaf. Below these, down to the lower epi- 
dermis, for one-half to three-quarters of the thickness of 
the leaf, the cells are commonly spherical or irregular in 
figure and arrangement, and more loosely disposed, with 
numerous and large interspaces. 

The interspaces among the leaf-cells are occupied with 
air, which is also, in most cases, the 
only content of the epidermal cells. 
The interior cells of the leaf are filled 
1L| with sap and contain the clilorophyl- 
sfftyKf granules. Under the microscope, these 
ttlSiyljfi are commonly seen attached to the walls 
"lil^B^lf^ of the cells, as in Fig. 56, or coating 
^^^SOkS grains of starch, or else floating free in 
the cell-sap. 

The structure of the veins or ribs of 

the leaf is similar to that of the vascular 

Fig. 56 bundles of the stem, of which they are 

branches. At a, Fig. 56, is seen the cross section of a 

vein in the bean-leaf. 




VEGETATIVE ORGANS OF PLANTS. 



309 



The epidermis, while often smooth, is frequently beset 
with hairs or glands, as seen in the figure. These are 
variously shaped cells, sometimes empty, sometimes, as 
in the nettle, filled with an irritating liquid. 

Leaf-Pores. — The epidermis of the mature leaf is pro- 
vided with avast number of " breathing pores," or stomata, 
by means of which the intercellular spaces in the interior 
of the leaf are brought into direct communication with 
the outer atmosphere. Each of these stomata consists 
usually of two curved guard-cells, which are disposed 

toward each other like the 
halves of an elliptical car- 
riage-spring. (Figs. 52 and 
53.) The opening between 
them is an actual orifice in 
the skin of the leaf. The 
size of the orifice is, how- 
ever, constantly changing, 
as the atmosphere becomes 
drier or more moist, and as 
the sunlight acts more or 
less intensely on its surface. In strong light they curve 
outwards, and the aperture is enlarged ; in darkness they 
straighten and shut together, like the springs of a heavily- 
loaded carriage, and nearly or entirely close the entrance. 
The effect of water usually is to 
close their orifices. 

In Fig. 56 is represented a section 
through the shorter diameter of a pore 
on the under surface of a bean-leaf. 
The air-space within it is shaded black. 
Unlike the other epidermal cells, those 
of the leaf -pores contain chlorophyll 
granules. 

Fig. 57 represents a portion of the epi- 
dermis of the upper surface of a potato- 
leaf, and Fig. 58 a similar portion of the 
under surface of the same leaf, magnified 
200 diameters. In both figures are seen the open stomata between the 
semi-elliptical cells. The outlines of the other epidermal cells are 




Fig. 57. 




Fig. 58. 



310 HOW CROPS GROW. 

marked by irregular double lines. The round bodies in the guard- 
cells of the pores are starch-grains, often present in these cells, when 
not existing in any other part of the leaf. 

The stomata are, with few exceptions, altogether want- 
ing on the submerged leaves of aquatic plants. On 
floating leaves they occur, but only on the upper surface. 
Thus, as a rule, they are not found in contact with 
liquid water. On the other hand, they are either absent 
from, or comparatively few in number upon, the upper 
surfaces of the foliage of land plants, which are exposed 
to the heat of the sun, while they occur abundantly on 
the lower sides of all green leaves. In number and size 
they vary remarkably. Some leaves possess but 800 to 
the square inch, while others have as many as 170,000 to 
that amount of surface. About 100,000 may be counted 
on an average-sized apple-leaf. In general, they are 
largest and most numerous on plants which belong to 
damp and shaded situations, and then exist on both sides 
of the leaf. 

The epidermis itself is most dense — consists of thick- 
walled cells and several layers of them — in case of leaves 
which belong to the vegetation of sandy soils in hot cli- 
mates. Often it is impregnated with wax on its upper 
surface, and is thereby made almost impenetrable to 
moisture. On the other hand, in rapidly-growing plants 
adapted to moist situations, the epidermis is thin and 
delicate. 

Exhalation of Water-Vapor. — A considerable loss 
of water goes on from the leaves of growing plants when 
they are freely exposed to the atmosphere. The water 
thus lost exhales in the form of invisible vapor. The 
quantity of water exhaled from any plant may be easily 
ascertained, provided it is growing in a pot of glazed 
earthen or other impervious material. A metal or glass 
cover is cemented air-tight to the rim of the vessel, and 
around the stem of the plant. The cover has an open- 



VEGETATIVE ORGANS OE PLANTS. 311 

ing with a cork, through which weighed quantities of 
water are added from time to time, as required. The 
amount of exhalation during any given interval of time 
is learned with a close approach to accuracy by simply 
noting the loss of weight which the plant and pot 
together suffer. Hales, who first experimented in this 
manner, found that a vigorous sunflower, three and a 
half feet high, whose foliage had an aggregate surface of 
39 square feet, gave oh* 30 ounces av. of water in a space 
of 12 hours, during a very warm, dry day. The average 
"rate of perspiration" for 15 days, in July and August, 
was 20 ounces av. At night, with "any sensible, though 
small dew, the perspiration was nothing." Knop 
observed a maize-plant to exhale, between May 22d and 
September 4th, no less than 36 times its weight of water. 
Hellriegel (at Dahme, Prussia) found that summer 
w T heat and rye, oats, beans, peas, buckwheat, red clover, 
yellow lupine and summer colza, on the average exhaled 
300 grams of water for 1 gram of dry matter produced 
above ground, during the entire season of growth, when 
stationed in a sandy soil. {Die Methode der Sandkultur, 
p. 662.) 

Exhalation is not a regular or uniform process, but 
varies with a number of circumstances and conditions. 
It depends largely upon the dryness and temperature of 
the air. When the air is in the state most favorable to 
evaporation, the loss from the plant is rapid and large. 
When the air is loaded with moisture, as during dewy 
nights or rainy weather, then exhalation is nearly or 
totally checked. 

The temperature of the soil, and even its chemical 
composition, the condition of the leaf as to its texture, 
age, and number of stomata, likewise affect the rate of 
exhalation. 

Exhalation is rather incidental than necessary to the 
life of many plants, since it may be suppressed or reduced 



312 



HOW CROPS GROW. 



to a minimum, as in a Wardian case or fernery, without 
evident influence on growth ; but plants of parentage 
naturally accustomed to copious exhalation of water 
flourish best where the conditions are favorable to this 
process. Exhalation is not injurious, unless the loss 
be greater than the supply. If water escapes from the 
leaves faster than it enters the roots, the succulent organs 
soon wilt, and if this disturbance 
goes on too far the plant dies. 

Exhalation ordinarily proceeds to 
a large extent from the surface of 
the epidermal cells. Although the 
cavities of these cells are chiefly oc- 
cupied with air, their thickened walls 
transmit outward the w r ater which is 
supplied to the interior of the leaf. 
Otherwise the escape of vapor occurs 
through the stomata. These pores 
appear to have the function of facil- 
itating exhalation, by their property 
of opening when exposed to sunlight. 
Thus evaporation from the leaves is 
favored at the time when root-action 
is most vigorous, and the plant is to 
the greatest degree surcharged with 
water. 

Access of Air to the Interior 
of the Plant. — Not only does the 
leaf allow the escape of vapor of water, but it admits of 
the entrance and exit of gaseous bodies. 

The particles of atmospheric air have easy access to 
the interior of all leaves, however dense and close their 
epidermis may be, however few or small their stomata. 
All leaves are actively engaged in absorbing or exhaling 
certain gaseous ingredients of the atmosphere during 
the whole of their healthy existence. 




Fte. 59. 



REPRODUCTIVE ORGANS OF PLANTS. 313 

The entire plant is, often, pervious to air through 
the stomata of the leaves. These communicate with the 
intercellular spaces of the leaf, which are, in general, 
occupied exclusively with air, and these again connect 
with the ducts which ramify throughout the veins of the 
leaf and branch from the vascular bundles of the stem. 
In the bark or epidermis of woody stems, as Hales long 
ago discovered, pores or cracks exist, through which 
the air has communication with the longitudinal ducts. 

These facts admit of demonstration by simple means. Sachs employs 
for this purpose an apparatus consisting of a short, wide tube of glass, 
B, Fig. 59, to which is adapted, below, by a tightly-fitting cork, a bent 
glass tube. The stem of a leaf is passed through a cork which is then 
secured air-tight in the other opening of the wide tube, the leaf itself 
being included in the latter, and the joints are made air-tight by smear- 
ing with tallow. The whole is then placed in a glass jar containing 
enough water to cover the projecting leaf -stem, and mercury is quickly 
poured into the open end of the bent tube, so as nearly to fill the lat, 
ter. The pressure of the column of this dense liquid immediately 
forces air into the stomata of the leaf, and a corresponding quantity is 
forced on through the intercellular spaces and through the vein ducts 
into the ducts of the leaf-stem, whence it issues in fine bubbles at S. 
It is even easy in many cases to demonstrate the permeability of the 
leaf to air by immersing it in water, and, taking the leaf -stem between 
the lips, produce a current by blowing. In this case the air escapes 
from the stomata. 

The air-passages of the stem may be shown by a similar arrange- 
ment, or in many instances, as, for example, with a stalk of maize, by 
simply immersing one end in water and blowing into the other. 

On the contrary, roots are destitute of any visible 
external pores, and are not pervious to air or vapor in 
the sense that leaves and young stems are. 

The air passages in the plant correspond roughly to 
the mouth, throat, and breathing cavities of the animal. 
We have, as yet, merely noticed the direct communica- 
tion of these passages with the external air by means of 
microscopically visible openings. But the cells which 
are not visibly porous readily allow the access and egress 
of water and of gases by osmose. To the mode in which 
this is effected we shall recur on subsequent pages. 

The Offices of Foliage are to put the plant in com- 
munication with the atmosphere and with the sun. On 



314 HOW CROPS GROW. 

the one hand it permits, and to a certain degree facili- 
tates, the escape of the water which is continually 
pumped into the plant by its roots, and on the other 
hand it absorbs, from the air that freely penetrates it, 
certain gases which furnish the principal materials for 
the construction of vegetable matter. We have seen that 
the plant consists of elements, some of which are volatile 
at the heat of ordinary fires, while others are fixed at 
this temperature. When a plant is burned, the former, 
to the extent of 90 to 99 per cent of the plant, are con- 
verted into gases, the latter remain as ashes. 

The reorganization of vegetation from the products of 
its combustion (or decay) is, in its simplest phase, the 
gathering by a new plant of the ashes from the soil 
through its roots, and of these gases from the air by its 
leaves, and the compounding of these comparatively sim- 
ple substances into the highly complex ingredients of the 
vegetable organism. Of this work the leaves have by 
far the larger share to perform ; hence the extent of 
their surface and their indispensability to the welfare of 
the plant. 



CHAPTER IV. 
EEPRODUCTIVE ORGANS OF PLANTS. 

MODES OF REPRODUCTION". 

Plants are reproduced in various ways. The simplest 
cellular plants have no evident special organs of repro- 
duction, but propagate themselves solely by a process of 
division which begins in the protoplasm, as already de- 
scribed in case of Yeast, p. 253. The lower so-called 
flowerless plants {Cryptogams), including molds, blights, 
mildews, mushrooms, toadstools (Fungi), mosses, lichens, 



REPRODUCTIVE ORGANS OF PLAXTS. 315 

etc., reproduce themselves in part by spores, each of 
which is a single minute cell that is capable of develop- 
ing into a plant like that from which it was thrown off. 

In very many cases a portion or "cutting" of root, 
stem or leaf, from herb or tree, placed in moist, warm 
earth, will grow and develop into a new plant in all 
respects similar to the original. The potato, grape, 
banana, and sugar-cane plants are almost exclusively 
propagated in this manner. In budding and grafting a 
portion of stem, carrying a single bud or a number of 
buds (scion), is planted, not in the soil, but in the cam- 
bial layer of a living root or stem with which it unites 
and thenceforward grows. 

The higher orders of plants (Phanerogams) have spe- 
cial reproductive organs, constituting or contained in 
their flowers, whose office it is to produce seed, the essen- 
tial part of which is the embryo, a ready-formed minia- 
ture plant which may grow into the full likeness of its 
parent. 

§2- 

THE FLOWER. 

In the higher plants the onward growth of the stem or 
of its branches is not necessarily limited, until from the 
terminal buds, instead of leaves, only flowers unfold. 
When this happens, as is the case with most annual and 
biennial plants, raised on the farm or in the garden, the 
vegetative energy has usually attained its fullest develop- 
ment, and the reproductive function begins to prepare 
for the death of the individual by providing seeds which 
shall perpetuate the species. 

There is often at first no apparent difference between 
the leaf-buds and flower-buds, but commonly, in the later 
stages of their growth, the latter are to be readily dis- 
tinguished from the former by their greater size, and by 
peculiar shape or color- 



316 



HCW CKOPS GROW. 



The Flower is a short branch, bearing a collection of 
organs, which, though usually having little resemblance 
to foliage, may be considered as leaves, more or less mod- 
ified in form, color, and office. 

The flower commonly presents four different sets of 
organs, viz., Calyx, Corolla, Stamens, and Pistils, and is 
then said to be complete, as in case of the apple, potato, 
and many common plants. Fig. 60 represents the com- 
plete flower of the Fuchsia, or ladies' ear-drop, now uni- 
versally cultivated. In Fig. 01 the same is shown in 
section. 

The Calyx (cup) ex, is the outermost floral envelope. 
Its color is red or white in the Fuchsia, though generally 
it is green. When it consists of several distinct leaves, 

they are called 

sepals. The calyx 

is frequently small 

and inconspicu- 
ous. In some 

cases it falls away 

as the flower 

opens. In the 

Fuchsia it firmly 

adheres at its base 

■ to the seed-vessel, 

land is divided into 

four lobes. 
The Corolla 

(crown), c, or ca, 

is one or several 

series of leaves 

which are situated 
within the calyx. It is usually of some other 'than a 
green color (in the Fuchsia, purple, etc.), often has 
marked peculiarities of form and great delicacy of struc- 
ture, and thus chiefly gives beauty to the flower. When 





Fig. 80. 



Fte. 61. 



REPRODUCTIVE ORGANS OF PLANTS. 317 

the corolla is divided into separate leaves, these are 
termed petals. The Fuchsia has four petals, which are 
attached to the calyx-tube. 

The Stamens, s, in Figs. 60 and 61, are generally 
slender, thread-like organs, terminated by an oblong 
sack, the anther, which, when the flower attains its full 
growth, discharges a fine yellow or brown dust, the so- 
called pollen. 

The anthers, as well as the grains of pollen, vary inform with nearly 
every kind of plant. The yellow pollen of Pine and Spruce is not in- 
frequently transported by the wind to a great distance, and when 
brought down by rain in considerable quantities, has been mistaken 
for sulphur. 

The Pistil, p, in Figs. 60 and 61, or pistils, occupy 
the center of the perfect flower. They are exceedingly 
various in form, but always have at their base the seed- 
vessels, or ovaries, ov, in which are found the ovules or 
rudimentary seeds. The summit of the pistil is desti- 
tute of the epidermis which covers all other parts of the 
plant, and is termed the stigma, st. 

As has been remarked, the floral organs may be consid- 
ered to be modified leaves ; or rather, all the appendages 
of the stem — the leaves and the parts of the flower to- 
gether — are different developments of one fundamental 
structure. 

The justness of this idea is sustained by the transform- 
ations which are often observed. 

The Rose in its natural state has a corolla consisting 
of five petals, but has a multitude of stamens and pistils. 
In a rich soil, or as the effect of those agencies which are 
united in "cultivation," nearly all the stamens lose their 
reproductive function and proper structure, and revert 
to petals ; the flower becoming "double." The tulip, 
poppy, and numerous garden-flowers, illustrate this in- 
teresting metamorphosis, and in these flow r ers we may 
often see the various stages intermediate between the 
perfect petal and the unaltered stamen. 



318 HOW CROPS GROW. 

On the other hand, the reversion of all the floral 
organs into ordinary green leaves has been observed not 
infrequently, in case of the rose, white clover, and other 
plants. 

While the complete flower consists of the four sets of 
organs above described, only the stamens and pistils are 
essential to the production of seed. The latter, accord- 
ingly, constitute a perfect flower, even in the absence of 
calyx and corolla. 

The flower of buckwheat has no corolla, but a white or 
pinkish calyx. 

The grasses have flow r ers in which calyx and corolla are 
represented by scale-like leaves, which, as the plants ma- 
ture, become chaff. 

In various plants the stamens and pistils are borne on 
separate flowers. Such are called monoecious plants, of 
which the birch and oak, maize, melon, squash, cucum- 
ber, and often the strawberry, are examples. 

In case of maize, the staminate flowers are the " tas- 
sels "at the summit of the stalk; the pistillate flowers 
are the young ears, the pistils themselves being the 
" silk," each fiber of which has an ovary at its base, that, 
if fertilized, develops to a kernel. 

Dioecious plants are those which bear the staminate 
(male, or sterile) flowers and the pistillate (female, or 
fertile) flowers on different individuals ; the willow, the 
hop-vine, and hemp, are of this kind. 

Nectaries are special organs — glands or tubes — secret- 
ing a sugary juice or nectar, which serves as food to 
insects. The clovers and honeysuckles furnish familiar 
examples. 

Fertilization and Fructification. — The grand func- 
tion of the flower is fructification. For this purpose 
pollen must fall upon or be carried by wind, insects, or 
other agencies, to the naked tip of the pistil. Thus sit- 
uated, each pollen-grain sends out a slender microscopic 



REPRODUCTIVE ORGANS OF PLANTS. 



319 



tube which penetrates the interior of the pistil until it 
enters the seed-vessel and comes in contact with the ovule 
or rudimentary seed. This contact being established, 
the ovule is fertilized and begins to grow. Thencefor- 
ward the corolla and stamens usually wither, while the 
base of the pistil and the included ovules rapidly increase 
in size until the seeds are ripe, when the seed-vessel falls 
to the ground or else opens and releases its contents. 

Fig. 62 exhibits the process of fertilization as observed 
in a plant allied to buckwheat, viz., the Polygonum con- 
volvulus. The cut represents a magnified section length- 
wise through the short pistil ; a is the stigma or summit 
of the pistil ; b are grains of pollen ; 
c are pollen tubes that have penetrated 
into the seed-vessel which forms the 
base of the pistil ; one has entered the 
mouth of the rudimentary seed, g, and 
reached the embryo sack, e, within 
which it causes the development of a 
germ ; d represents the interior wall 
of the seed-vessel ; h, the base of the 
seed and its attachment to the seed- 
vessel. 

Self-Fertilization occurs when 
ovules are impregnated by pollen 
from the same flower. In many plants 
self-fertilization is favored by the posi- 
tion of the organs concerned. In the 
pendent flower of the Fuchsia as well Fi £- 62 - 

as in the upright one of the strawberry the stigma is just 
below and surrounded by the anthers, so that when the 
mature pollen is discharged it cannot fail to fall upon the 
stigma. Some flowers, as those of the closed gentian 
{Gentiana Andrew sii) and the small subterranean blos- 
soms of sheep-sorrel (Oxalis acetosella), touch-me-not 
(Impatiens), and of many violets, never open, and not 




320 HOW CROPS GROW. 

only are self-fertile but cannot well be otherwise. Some 
plants which carry these closed and inconspicuous subter- 
ranean flowers depend upon them for reproduction by 
seed, their large and showy serial flowers being often bar- 
ren, as in violets, or totally infertile ( Voandzeia.) Flax 
and turnips are self-fertilizing. 

Cross-Fertilization results from the contact of the 
pollen of one flower with the ovules of another. In many 
plants remarkable arrangements exist that hinder or 
totally prevent self-fertilization and favor or ensure cross- 
fertilization. 

In monoecious plants, as hazel or squash, flowers of one 
sort yield pollen, others, different, contain the ovules ; 
so that two distinct and more or less distant blossoms of 
the same plant are necessary for seed-production. 

In the dioecious poplar and hops, the plant that pro- 
duces pollen never carries ovules and that which bears the 
latter is destitute of the former, so that two distinct 
plants must co-operate to form seeds. 

It often happens that the pollen of a flower cannot fer- 
tilize the ovules of the same flower. This may be either 
because the stigma is behind the pollen in development, 
as in case of various species of geranium, or because the 
stigma has passed its receptive period before the pollen is 
mature, as in Sweet Vernal Grass (Anthoxanthum odo- 
ratum). In both instances the ripened pollen may reach 
stigmas that are ready in other flowers and fertilize their 
ovules, insects being often the means of transportation. 

In a large number of flowers, whose pollen and stigmas 
are simultaneously prepared, the position of the organs 
is such that self-fertilization is difficult or impossible. 
The Iris, Crocus, Pansy, Milk- weed (Asriepias), and many 
Orchids, are of this class. The offices of insects in search 
of nectar, or attracted by odors, are here indispensable. 
The common red clover cannot produce seed without 
insect aid, and the bumblebee customarily performs this 



REPRODUCTIVE ORGANS OF PLANTS. 321 

service. The insect, in exploring a flower for nectar, 
leaves upon its stigma pollen taken from the flower last 
visited, and in emerging renews its burden of pollen to 
bestow it in turn upon the stigma of a third flower. 

Cross-fertilization is doubtless often effected by insects 
in case of flowers which are in all respects adapted for 
self-fertilization, while flowers that casual examination 
would pronounce self-fertile are in fact of themselves 
sterile. The flowers of rye open singly, the long stamens 
shortly mature and discharge their pollen, which falls on 
the stigmas of flowers standing lower in the same head, 
or on neighboring heads. According to Rimepare, the 
individual rye-flower can fertilize neither itself nor the 
different flowers of an ear, nor can the different ears of 
one and the same plant pollinate one another with suc- 
cess, although no mechanical hindrance exists. (Sachs, 
Physiology of Plants, p. 700.) 

Results of Self-Fertilization and Cross-Fertili- 
zation. — Sprengel, one of the early students of Plant- 
Reproduction, wrote in 1793, " Nature appears to be 
unwilling that any flower shall be fertilized by its own 
pollen." Extensive observation indicates decidedly 
that cross-fertilization is far more general than self- 
fertilization, especially among the higher plants. Dar- 
win has shown that, in many cases, the pollen of a flower 
is incapable of fertilizing its own ovules, and that the 
pollen from another flower of the same plant is scarcely 
more potent. In these cases the pollen from a flower 
borne by another plant of the same kind is potent, and 
the more so the m.ore tinlike the two plants are. 

In Darwin's trials on the reproduction of the Morning 
Glory, Ipomea purpurea, carried out through ten gener- 
ations, the average height of 73 self-fertilized plants was 
66 inches, while that of the same number of crossed 
plants was 85.8 inches, or in the ratio of 77 to 100. 
The relative number of seeds produced by the self-fertil- 
21 



322 HOW CROPS GKOVV. 

ized and cross-fertilized plants in the 1st, 3d, and 9th 
generations were respectively as 64 to 100 ; 35 to 100, 
and 26 to 100. 

In other cases, but, so far as observed, much less com- 
monly, self-fertilization gives the best results both as 
regards numbers and vigor of offspring. In Darwin's ex- 
periments a variety of Mimulus luteus originated, of 
which the self-fertilized progeny surpassed the cross-fer- 
tilized, during several generations. In the seventh gen- 
eration the ratio of superiority of the self-fertilized, as 
regards numbers of fruit, was as 137 to 100, and in respect 
to size of plants as 126 to 100. 

Continued self-fertilization, is thus limited by its ten- 
dency, as statistically determined, to reduce both the 
vegetative and reproductive vigor of the plant. On the 
other hand, cross- fertilization is possible or practicable 
only within very narrow bounds, and the increased pro- 
ductiveness that follows it soon reaches a limit, as is 
shown by the history of vegetable hybrids. 

That neither mode of fertilization is exclusively or speci- 
ally adapted to the highest development of plants in gen- 
eral, or of particular kinds of plants, is shown by the fact 
that in the course of Darwin's researches on the Ipo?nea 
2mrpurea, just referred to, in the sixth generation a self- 
fertilized plant (variety) appeared, which was superior to 
its crossed collateral, and was able to transmit its vigor 
and fertility to its descendants. 

It is evident, therefore, that the causes which lead to 
higher development co-operate most fully, sometimes in 
the one, sometimes in the other, mode of impregnation 
and do not necessarily belong to either. We must be- 
lieve that excellence in offspring is the result of excel- 
lence in the parents, no matter what lines their heredity 
may have followed, except as these lines have influenced 
their individual excellence. That crossing commonly 
gives better offspring than in-and-in breeding is due to 



REPRODUCTIVE ORGANS OF PLANTS. 323 

the fact that in the latter both parents are likely to pos- 
sess by inheritance the same imperfections, which are 
thus intensified in the progeny, while in cross-breeding 
the parents more usually have different imperfections 
which often, more or less, compensate each other in the 
immediate descendants. 

Hybridizing.— As the sexual union of quite different 
kinds of animals sometimes results in the birth of a 
hybrid, so, among plants, the ovules of one kind (spe- 
cies, or even genus) may be fertilized by the pollen of 
another different kind, and the seed thus developed, in 
its growth produces a hybrid plant. As in the animal, 
so in the vegetable kingdom, the range within which 
hybridization is possible appears to be very narrow. It 
is only between rather closely allied plants that fecunda- 
tion can take place, and the more close the resemblance 
the more ready and fruitful the result. Wheat, rye, 
and barley, in ordinary cultivation, show no tendency to 
"mix ;" the pollen of one of these similar plants rarely 
fertilizing* the ovules of the others. But external sim- 
ilarity is no certain mark of capacity for hybridization. 
The apple and pear have never yet been crossed, while 
the almond and nectarine readily form hybrids. (Sachs. ) 

Hybrids are usually less productive of seeds than the 
parent plants, and sometimes are entirely sterile, but, on 
the other hand, they are often more vigorous in their 
vegetative development — produce larger and more numer- 
ous leaves, flowers, roots, and shoots, and are longer- 



on the first edition was written, "being incapable of fertilizing." 
The experiments of Mr. Carman have lately shown that wheat and 
rye may be made to produce fertile hybrids. A beardless wheat was 
fertilized by rye-pollen and produced nine seeds, eight of which were 
fully fertile, one nearly sterile. The last yielded 20 beads, which bore 
only a few grains. Tlie plants from the nine fertile seeds were polli- 
nated again with rye and produced but a few fertile seeds. A few 
plants, seven-eighths rye, were finally produced, which were, however, 
totally sterile. Of the three-fourths cross, fertile progeny has been 
raised for several years, and the characters of this genus-hybrid ap- 

Sear to be nearlv fixed, though occasionally a sterile head appears. — 
ural New Yorker, 1883, p. 644. 



324 HOW CROPS GROW. 

lived than their progenitors. For this reason hybrids 
are much valued in fruit- and flower-culture. 

Some genera of plants have great capacity for produc- 
ing hybrids. The Vine and the Willow are striking 
examples. The cultivated Vine of Europe and Western 
Asia is Vitis vinifera. In the United States some 
twelve distinct species are found, of which three, Vitis 
riparia, Vitis aestivalis, and Vitis labrusca, are native to 
New England. Nearly all these kinds of grape cross 
with such readiness that scores of new hybrids have been 
brought into cultivation. "The kinds now known as 
Clintou, Taylor, Elvira, Franklin, are hybrids of V. 
riparia and V. labrusca. York-Madeira, Eumelan, 
Alvey, Morton's Virginia, Cynthiana, are crosses of V. 
labrusca and V. aestivalis. Delaware is a hybrid of V. 
labrusca, V. vinifera, and V. aestivalis. Herbemont, 
Rulander, and Cunningham are hybrids of V. aestivalis, 
V. cinerea, and V. vinifera. The vine known in France 
as " Gaston -Bazille " is a hybrid of V. labrusca, V. aesti- 
valis, V. rupestris, and V. riparia."* The foregoing 
are "spontaneous wild hybrids." The "Rogers Seed- 
lings," including Salem, Wilder, Barry, Agawam, Mas- 
iasoit, etc., are examples of artificial hybrids of V. vin- 
ifera and V. labrusca. 

Hybridization between plants is effected, if at all, by 
removing from the flower of one kind the stamens 
before they shed their pollen, and dusting the summit 
of the properly-matured pistil with pollen from another 
kind. Commonly, when two plants hybridize, the pollen 
of either will fertilize the ovules of the other. In some 
cases, however, two plants yield hybrids by only one 
order of connection. 

The mixing of different Varieties, as commonly hap- 
pens among maize, melons, etc., is not hybridization, 



*Millardet in Sachs's Lectures on the Physiology of Plants, 1887, p. 785. 



REPRODUCTIVE ORGANS OF PLANTS. 325 

in the long-established sense of this word, but rather 
"cross-breeding." The two processes are, however, fun- 
damentally the same, and their results are sufficiently 
distinguished by the terms Species-hybrid, or Genus- 
hybrid, and Variety-hybrid. We are thus led to brief 
notice of the meaning of the terms Species and Vari- 
ety, and of the distinctions employed in Botanical 
Classification. 

Species. — Until recently naturalists generally held 
the view that in " the beginning" certain kinds of plants 
and animals were separately created, with the power to 
reproduce their own kind, but incapable of fertile hybrid- 
ization, so that only such original kinds could be per- 
petuated. Such supposed original kinds were called 
Species. At present, on the contrary, most biologists 
regard all existing kinds of plants and animals as prob- 
ably the results of a very slow and gradual development 
or evolution from one vastly remote ancestor of the sim- 
plest type. On this view a Plant-Species comprises a 
number of individuals, "among which we are unable to 
distinguish greater differences than experience shows us 
we should find among a number of plants raised from 
the seed of the same parent." 

On the former view, plants yielding fertile l^brids or 
crosses must be Varieties of the same species. On the 
latter view different Species may hybridize. They are 
not originally different, and by Evolution or Eeversion 
may pass into each other. On either view, the distinc- 
tion of plants into species is practically the same, being 
largely a matter of expert judgment or agreement among 
authorities, and not capable of exact decision by refer- 
ence to fixed rules or known natural laws. The charac- 
ters that are taken to be common to all the individuals 
of a species are termed specific characters. The differ- 
ences used to divide plants into species are called specific 
differences. 



320 HOW CROPS GROW. 

Naturalists, acting under the older view, attempted to 
draw specific characters more finely than is now thought 
practicable. Many plants formerly described as separate 
species are now united together into a single species, 
the various forms at first supposed to be specifically or 
originally distinct having been shown to be of common 
origin, either by producing them from each other or by 
observing that thev were connected through a series of 
intermediate forms, insensibly grading into each other. 
Varieties. — The individuals of any "species" differ. 
In fact, no two individuals are quite alike. Circum- 
stances of climate, soil, and situation increase these dif- 
ferences, and varieties originate when such differences 
are inherited and in the progeny assume a comparative 
'permanence. But as external conditions cause variation 
away from any particular representative of a species, so 
they may cause variation back again to the original type. 
Varieties most commonly originate in propagation by 
seed, especially in case of the trees or plants commonly 
cultivated for their fruit. Seedling grapes, apples,, or 
potatoes are very likely to differ from their parents. 
Seed which has been imperfectly ripened or long kept is 
said to be prone to yield new varieties. 

Less frequently variations arise in propagation by 
cuttings, buds, grafts, or tubers. Pinks and Pelargo- 
niums in the florist's hands are prolific of these "sports." 
The causes that produce varieties are probably numer- 
ous, but in many cases their nature and their mode of 
action is obscure or unknown. Scarcity or abundance 
of nutriment, we can easily comprehend, may, on the one 
hand, dwarf a plant, or, on the other, lead to the pro- 
duction of a giant individual; but how, in some cases, 
the peculiarities thus impressed upon individuals become 
fixed, and are transmitted to subsequent generations, 
while in others they disappear, is difficult to explain. 
Varieties may often be perpetuated for a long time by 



REPRODUCTIVE ORGANS OF PLANTS. 327 

the seed. This is true of our cereal and leguminous 
plants, which commonly reproduce their kind with strik- 
ing regularity. Varieties of some plants cannot, with 
certainty, be reproduced unaltered by the seed, but are 
continued in the possession of their peculiarities by cut- 
tings, layers, and grafts. The fact that the seeds of a 
potato, a grape, an apple, or pear cannot be depended 
upon to reproduce the "variety, may perhaps be more 
commonly due to unavoidable contact of pollen from 
other varieties (variety-hybridization) than to inability 
of the mother plant to perpetuate its peculiarities. 
That such inability often exists is, however, well estab- 
lished, and is, in general, most obvious in case of varie- 
ties that have, to the greatest degree, departed from the 
original specific type and of course, in sterile hybrids. 

The sports which originate in the processes of propa- 
gating from buds (grafts, tubers, cuttings) are perpet- 
uated by the same processes. ^ 

Species and Varieties, as established in our botanical 
literature, are exemplified by the Vine, whose species are 
vinifera, riparia, Ictbrusca, etc., and some of whose 
North American Varieties, the results of hybridization, 
have already been enumerated. 

Genus (plural Genera). — Species which resemble 
each other in most important points of structure are 
grouped together by botanists into a genus. Thus the 
various species of oaks, — white, red, black, scrub, live, 
etc., — taken together, form the Oak-genus Quercus, 
which has a series of characters common to all oaks 
(generic characters), that distinguishes them from every 
other kind of tree or plant. 

Families, or Orders, in botanical language, are 
groups of genera that agree in certain particulars. Thus 
the several plants well-known as mallows, hollyhock, 
okra, and cotton, are representatives of as many different 
genera. They all agree in a number of points, especially 



328 HOW CROPS GROW. 

as regards the structure of their fruit. They are accord- 
ingly grouped together into a natural family or order, 
which differs from all others. 

Classes, Series, and Classification. — Classes are 
groups of orders, and Series are groups of classes. In 
botanical classification, as now universally employed — 
classification after the Natural System — all plants are 
separated into two series, as follows : 

1. Flowering Plants (Phanerogams), which produce 
flowers and seeds with embryos, and 

2. Flowerless Plants (Cryptogams), that have no 
proper flowers nor seeds, and are reproduced, in part, 
by spores which are in most cases single cells. This 
series includes Ferns, Horse-tails, Mosses, Liverworts, 
Lichens, Sea-weeds, Mushrooms, and Molds. 

It was believed, until recently, that there exists a sharp and abso- 
lute distinction between flowering and flowerless plants, but our 
larger knowledge now recognizes that here, as among genera, species, 
and varieties, kinds merge or shade into each other. 

The use of Classification is to give precision to our 
notions and distinctions, and to facilitate the using and 
acquisition of knowledge. Series, classes, orders, genera, 
species, and varieties are as valuable to the naturalist as 
pigeon-holes are to the accountant, or shelves and draw- 
ers to the merchant. 

Botanical Nomenclature. — The Latin or Greek 
names which botanists employ are essential for the dis- 
crimination of plants, being equally received in all coun- 
tries, and belonging to all languages where science has a 
home. They are made necessary, not only by the confu- 
sion of tongues, but by confusions in each vernacular. 

Botanical usage requires for each plant two names, 
one to specify the genus, another to indicate the species. 
Thus all oaks are designated by the Latin word Quercus, 
while the red oak is Quercus rubra, the white oak is 
Quercus alba, the live oak is Quercus virens, etc. 



REPRODUCTIVE ORGANS OF PLANTS. 329 

The designation of certain important families of plants 
is derived from a peculiarity in the form or arrangement 
of the flower. Thus the pulse family, comprising the 
bean, pea, and vetch, as well as alfalfa and clover, are 
called Papilionaceous plants, from the resemblance of 
their flowers to a butterfly (Latin, papilio). Again, the 
mustard family, including the radish, turnip, cabbage, 
w r ater-cress, etc., are termed Cruciferous plants, because 
their flowers have four petals arranged like the four arms 
of a cross (Latin, crux). 

The flowers of a large natural order of plants are 
arranged side by side, often in great numbers, on the 
expanded extremity of the flower stem. Examples are 
the thistle, dandelion, sunflower, artichoke, China-aster, 
etc., which, from bearing such compound heads, are 
called Composite plants. 

The Coniferous (cone-bearing) plants comprise the 
pines, spruces, larches, hemlocks, etc., whose flowers are 
arranged in conical receptacles. 

The flowers of the carrot, parsnip, and caraway are 
stationed at the extremities of stalks which radiate from 
a central stem like the arms of an umbrella ; hence they 
are called Umbelliferous plants (from umbel, Latin for 
little screen). 

§2. 

THE FRUIT. 

The Fruit comprises the seed-vessel and the seeds, to- 
gether with their various appendages. 

Fruits are either dehiscent when the seed-vessel opens 
and sheds the seed or are indehiscent when it remains 
closed. 

The seed-vessel, consisting of the base of the pistil in 
its matured state, exhibits a great variety of forms and 
characters, which serve, chiefly, to define the different 



330 HOW CROPS GROW. 

kinds of Fruits. Of these- we shall only adduce such as 
are of common occurrence and belong to the farm. 

The Nut has a hard, leathery or bony indehiscent 
shell, that usually contains a single seed. Examples are 
the acorn, chestnut, beech-nut, and hazel-nut. The cup 
of the acorn and the bur or shuck of the others is a sort 
of fleshy calyx. 

The Stone-fruit, or Drupe, is a nut enveloped by a 
fleshy or leathery coating, like the peach, cherry, and 
plum, also the butternut and hickory-nut. Easpberries 
and blackberries are clusters of small drupes. 

Pome is a term applied to fruits like the apple and 
pear, the core of which is the true seed-vessel, originally 
belonging to the pistil, while the often edible flesh is the 
enormously enlarged and thickened calyx, whose with- 
ered tips are always to be found at the end opposite the 
stem. 

The Berry is a many-seeded fruit of which the entire 
seed-vessel becomes thick and soft, as the grape, currant, 
tomato, and huckleberry. 

Gourd fruits have externally a hard rind, but are 
fleshy in the interior. The melon, squash, and cucum- 
ber are of this kind. 

The Akene is a fruit contnining a single seed which 
does not separate from its dry envelop. The so-called 
seeds of the composite plants — for example, the sunflower, 
thistle, and dandelion — are akenes. On removing the 
outer husk or seed-vessel we find within the true seed. 
Many akenes are furnished with a pappus, a downy or 
hairy appendage, the remains of the calyx, as seen in the 
thistle, which enables the seed to float and be carried 
about in the wind. The fruit or grain of buckwheat is 
akene-like. 

The Grains are properly fruits. Wheat, rye, and 
maize consist of the seed and the seed-vessel closely 
united. When these grains are ground, the bran that 



REPRODUCTIVE ORGANS OF PLANTS. 331 

comes off is the seed-vessel together with the outer coat- 
ings of the seed. Barley-grain, in addition to the seed- 
vessel, has the petals of the flower or inner chaff, and 
oats have, besides these, the calyx or outer chaff adher- 
ing to the seed. 

Pod is the name properly applied to any dry seed-ves- 
sel which opens and scatters its seeds when ripe. Sev- 
eral kinds have received special designations ; of these 
we need only notice one. 

The Legume is a pod, like that of the bean, which 
splits into two halves, along whose inner edges seeds are 
borne. The pulse family, or papilionaceous plants, are 
also termed leguminous, from the form of their fruit. 

The Seed, or ripened ovule, is borne on a stalk which 
connects it with the seed-vessel. Through this stalk it 
is supplied with nutriment while growing. When ma- 
tured and detached, a scar commonly indicates the point 
of former connection. 

The seed has usually two distinct coats or integuments. 
The outer one is often hard, and is generally smooth. 
In the case of cotton-seed it is covered with the valuable 
cotton fiber. The second coat is commonly thin and 
delicate. 

The Kernel lies within the integuments. In many 
cases it consists exclusively of the embryo, or rudimen- 
tary plant. In others it contains, besides the embryo, 
what has received the name of endosperm. 

The Endosperm forms the chief bulk of all the 
grains. If we cut a seed of maize in two lengthwise, we 
observe, extending from the point where it was attached 
to the cob, the soft "chit," b, Fig. 63, which is the em- 
bryo, to be presently noticed. The remainder of the 
kernel, a, is endosperm ; the latter, therefore, yields in 
great part the flour or meal which is so important a part 
of the food of man and animals. 

The endosperm is intended for the support of the 



332 HOW CROPS GROW. 

young plant as it develops from the embryo, before it is 
capable of depending on the soil and atmosphere for sus- 
tenance. It is not, however, an indispensable part of the 
seed, and may be entirely removed from it, without 
thereby preventing the growth of a new plant. 

The Embryo, or Germ, is the essential and most 
important portion of the seed. It is, in fact, a ready- 
formed plant in miniature, and has its root, stem, leaves, 
and a bud, although these organs are often as undevel- 
oped in form as they are in size. 

As above mentioned, the chit of the seeds of maize and 
the other grains is the embryo. Its form is with diffi- 
culty distinguishable in the dry seeds, but when they 
have been soaked for several days in water, it is readily 
removed from the accompanying endosperm, and plainly 
exhibits its three parts, viz., the Radicle, the Plumule, 
and the Cotyledon. 

In Fig. 63 is represented the embryo of maize. In A 
and B it is seen in section imbedded in the endosperm. 
C exhibits the detached embryo. The Radicle, r, is the 
stem of the seed-plant, its lower extremity is the point 
from which downward growth proceeds, and from which 
the first true roots are produced. The Plumule, c, is 
the central bud, out of which the stem, with new leaves, 
flowers, etc., is developed. The Cotyledon, I, is in 
structure a ready-formed leaf, which clasps the plumule 
in the embryo, as the 
proper leaves clasp the ^ 
stem in the mature 




maize-plant. The coty- yb/A-c 

ledon of maize does not, 

however, perform the 

functions of a leaf ; on ig ' 

the contrary, it remains in ■ the soil during the act of 

sprouting, and its contents, like those of the endosperm, 

are absorbed by the seedling. The first leaves which ap- 



REPRODUCTIVE ORGANS OF PLANTS. 333 

pear above-ground, in the case of maize and the other 
grains (buckwheat excepted), are those which in the 
embryo were wrapped together in the plumule, where 
they can be plainly distinguished by the aid of a mag- 
nifier. 

It will be noticed that the true grains (which have 
sheathing leaves and hollow jointed stems) are monocot- 
yledonous (one-cotyledoned) in the seed. As has been 
mentioned, this is characteristic of plants with endoge- 
nous or inside-growing stems (p. 290). 

The seeds of the Exogens (outside-growers — p. 296) are 
dicotyledonous, i. e., have two cotyledons. Those of 
buckwheat, flax, and tobacco contain an endosperm. 
The seeds of nearly all other exogenous agricultural 
plants are destitute of an endosperm, and, exclusive of 
the coats, consist entirely of embryo. Such are the seeds 
of the Leguminosae, viz., the bean, pea, and clover; of 
the Cruciferse, viz., turnip, radish, and cabbage ; of ordi- 
nary fruits, the apple, pear, cherry, plum, and peach ; of 
the Gourd family, Viz. , the pumpkin, melon and cucum- 
ber • and finally of many hard-wooded trees, viz., the 
oak, maple, elm, birch, and beech. 

"We may best observe the structure of the two-cotyle- 
doned embryo in the ordinary garden- or kidney-bean. 
After a bean has been soaked in warm water for several 
hours, the coats may be easily removed, and the two 
fleshy cotyledons, c, c, in Fig. 64, are found separated 
from each other save at the point where the radicle, a, is 
seen projecting lik^ blunt spur. On 
carefully breaking away one of the coty- 
ledons, we get a side view of the radicle, 
a, and plumule, b, the former of which 
was partially and the latter entirely im- 
bedded between the cotyledons. The 
&g- 64 - plumule plainly exhibits two delicate 

leaves, on which the unaided eye may note the veins. 




334 HOW CROPS GROW. 

These leaves are folded together along their mid-ribs, and 
may be opened and spread out with help of a needle. 

When the kidney-bean (Phaseolus) germinates, the 
cotyledons are carried up into the air, where they become 
green and constitute the first pair of leaves of the new 
plant. The second pair are the tiny leaves of the plum- 
ule just described, between which is the bud, whence all 
the subsequent aerial organs develop in succession. 

In the horse-bean ( Vicia faba), as in the pea, the cot- 
yledons never assume the office of leaves, but remain in 
the soil and gradually yield a large share of their con- 
tents to the growing plant, shriveling and shrinking 
greatly in bulk, and finally falling away and passing into 
decay. 

VITALITY OF SEEDS AND THEIR INFLUENCE ON THE 
PLANTS THEY PRODUCE. 

Duration of Vitality. — In the mature seed the em- 
bryo lies dormant. The duration of its vitality is very 
various. The seeds of the willow, it is asserted, will not 
grow after having once become dry, but must be sown 
when fresh ; they lose their germinative power in two 
weeks after ripening. 

On the other hand, single seeds of various plants, as of 
sorrel (Oxalis strida), shepherd's purse (Thlaspi arv- 
ense), and especially of trees like the oak, beech, and 
cherry, remain with moist embryos many months or sev- 
eral years before sprouting. (Nobbe & Haenlein, Vs. 
St., XX, p. 79.) 

Among the seeds of various plants, clover for example, 
which, under favorable circumstances, mostly germinate 
within one or two weeks, may often be found a number 
which remain unchanged, sound and dry tvithin, for 
months or years, though constantly wet externally. The 



REPRODUCTIVE ORGANS OF PLANTS. 335 

outer coat of these seeds is exceptionally thick, dense, 
and resistant to moisture. If this coat be broken by the 
scratch of a needle the seed will shortly germinate. In a 
collection of such seeds, kept in water, individuals sprout 
from time to time. In case of common sorrel (Rumex 
acetosella), Nobbe & Haenlein found that 10 per cent of 
the seeds germinated between the 400th and 500th day 
of keeping in the sprouting apparatus. 

The appearance of strange plants in earth newly 
thrown out of excavations may be due to the presence of 
such resistant seed, which, scratched by the friction of 
the soil in digging, are brought to germination after a 
long period of rest. Lyell states that seeds of the yellow 
Nelumbo (water lily) have sprouted after being in the 
ground for a century, and R. Brown is authentically 
said to have germinated seeds of a Nelumbo taken by 
him from Hans Sloane's herbarium, where they had been 
kept dry for at least 150 years. 

The seeds of wheat usually, for the most part, lose their 
power of growth after having been kept from three to 
seven years. Count Sternberg and others are said to 
have succeeded in germinating wheat taken from an 
Egyptian mummy, but only after soaking it in oil. 
Sternberg relates that this ancient wheat manifested no 
vitality when placed in the soil under ordinary circum- 
stances, nor even when submitted to the action of acids 
or other substances which gardeners sometimes employ 
with a view to promote sprouting. 

Girardin claims to have sprouted beans that were over 
a century old. It is said that Grimstone with great pains 
raised peas from a seed taken from a sealed vase found in 
the sarcophagus of an Egyptian mummy, presented to 
the British Museum by Sir G. Wilkinson, and estimated 
to be near 3,000 years old. 

Yilmorin, from his own trials, doubts altogether the 
authenticity of the " mummy wheat," and it is probable 



336 HOW CROPS GROW. 

that those who have raised mummy wheat or mummy 
peas were deceived either by an admixture of fresh seed 
with the ancient, or by planting in ordinary soil, which 
commonly contains a variety of recent seeds that come 
to light under favorable conditions. 

Dietrich (Hoff. Jahr., 1862-3, p. 77) experimented 
with seeds of wheat, rye, and a species of Bromus, which 
were 185 years old. Nearly every means reputed to favor 
germination was employed, but without success. After 
proper exposure to moisture, the place of the germ was 
usually found to be occupied by a slimy, putrefying liq- 
uid. Commonly, among the freshest seeds, when put to 
the sprouting trial, some will mold or putrefy. 

The fact appears to be that the circumstances under 
which the seed is kept greatly influence the duration of 
its vitality. If seeds, when first gathered, be thoroughly 
dried, and then sealed up in air-tight vessels, there is no 
evident reason why their vitality should not endure for 
long periods. Moisture and the microbes that flourish 
where it is present, not to mention insects, are the agen- 
cies that usually put a speedy limit to the duration of 
the germinative power of seeds. 

In agriculture it is a general rule that the newer the 
seed the better the results of its use. Experiments have 
proved that the older the seed the more numerous the 
failures to germinate, and the weaker the plants it pro- 
duces. 

Londet made trials in 1856-7 with seed- wheat of the 
years 1856, '55, '54, and '53. The following table exhib- 
its the results : 

Number of stall's 
Per cent of seeds Length of leaves four days and earsper 
sprouted. after coming up. hundred seeds. 

Seed of 1853 none 

" » 1854 51 0.4 to 0.8 inches. 269 

" " 1855 73 1.2 " 365 

» » 1856 74 1.6 " 404 

The results of similar experiments made by Haberlandt 
on various grains are contained in the following table : 



REPRODUCTIVE ORGANS OF PLANTS. 337 

Per cent of seeds that germinated in 1861 from the years : 

1860 1851 1854 1855 1857 1858 1859 1860 

Wheat o o 8 4 73 eo 84 % 

Rye 48 100 

Barley 24 48 33 92 89 

Oats 60 56 48 72 32 80 96 

Maize not tried 76 56 not tried 77 100 97 

Results of the Use of Long-kept Seeds The 

fact that old seeds yield weak plants is taken advantage 
of by the florist in producing new varieties. It is said 
that while the one-year-old seeds of Ten-weeks Stocks 
yield single flowers, those which have been kept four 
years give mostly double flowers. 

In case of melons, the experience of gardeners goes 
to show that seeds which have been kept several, even 
seven years, though less certain to come up, yield plants 
that give the greatest returns of fruit ; while plantings 
of new seeds run excessively to vines. 

Unripe Seeds.— Experiments by Lucanus prove that 
seeds gathered while still unripe, — when the kernel is 
soft and milky, or, in case of cereals, even before starch 
has formed, and when the juice of the kernel is like 
water in appearance, — are nevertheless capable of germi- 
nation, especially if they be allowed to dry in connection 
with the stem (after-ripening). Such immature seeds, 
however, have less vigorous germinative power than 
those which are allowed to mature perfectly ; when sown, 
many of them fail to come up, and those which do, yield 
comparatively weak plants at first and in poor soil give a 
poorer harvest than well-ripened seed. In rich soil, 
however, the plants which do appear from unripe seed, 
may, in time, become as vigorous as any. (Lucanus, Vs. 
St., IV, p. 253.) 

According to Siegert, the sowing of unripe peas tends 
to produce earlier varieties. Liebig says: "The gar- 
dener is aware that the flat and shining seeds in the pod 
of the Stock Gillyflower will give tall plants with single 
flowers, while the shriveled seeds will furnish low plants 
with double flowers throughout. 22 



338 HOW CROPS GROW. 

Cobn found that seeds not fully ripe germinate some- 
what sooner than those which are more mature, and he 
believes that seeds in a medium stage of ripeness germi- 
nate most readily. 

Quick- and Slow-Sprouting Seeds. — When a con- 
siderable number of agricultural or garden seeds, fresh 
and of uniform appearance, are placed under favorable 
circumstances for germinating, it is usually observed 
that sprouting begins within two to ten days, and con- 
tinues for one or several weeks before all or nearly all 
the living embryos have manifestly commenced to grow. 
Nobbe (in 1886 and 1887) found in extensive trials with 
12 varieties of stocks, Matthiola annua, that the quick- 
sprouting seeds, which germinated in three to four days, 
yielded earlier and larger plants, which blossomed with 
greater regularity and certainty, and produced a pre- 
ponderance (82 per cent) of sterile double flowers, while 
the slow-sprouting seeds, that were ten to twelve days in 
germinating, gave smaller plants that came later to 
bloom, and yielded 73 per cent of fertile single flowers. 

Should continued trials prove these results to be of 
constant occurrence, it is evident that by breeding exclu- 
sively from the quick-sprouting seeds, the double-flower- 
ing varieties should soon become extinct, from failure to 
produce seed. On the other hand, exclusive use of the 
slow-sprouting seeds would extinguish the tendency to 
variation and double-blooming, which gives this plant 
its value to the florist. 

Dwarfed or Light Seeds. — Muller, as well as Hell- 
riegel, found in case of the cereals that light or small 
grain sprouts quicker but yields weaker plants, and is 
not so sure of germinating as heavy grain. 

Liebig asserts (Natural Laws of Husbandry, Am. 
Ed., 18G3, p. 24) that "poor and sickly seeds will pro- 
duce stunted plants, which will again yield seeds bearing 
in a great measure the same character." This is true 
"in the long run," i. e., small or light seeds, the result 



REPRODUCTIVE ORGANS OF PLANTS. 339 

of unfavorable conditions, will, under the continuance 
of those conditions, produce stunted plants (varieties), 
whose seeds will be small and light. (Compare Tuscan 
and pedigree wheat, p. 158.) 

Schubart, whose observations on the roots of agricul- 
tural plants are detailed in a former chapter (p. 263), 
says, as the result of much investigation, "the vigorous 
development of plants depends far less upon the size and 
weight of the seed than upon the depth to which it is 
covered with earth, and upon the stores of nourishment 
which it finds in its first period of life." Eeference is 
here had to the immediate produce under ordinary agri- 
cultural conditions. 

Value of Seed as Related to its Density From 

a series of experiments made at the Royal Agricultural 
College at Cirencester, in 1863-6, Church concludes that 
the value of seed-wheat stands in a certain connection 
with its specific gravity {Practice with Science, pp. 107, 
342, 345, London, 1867). He found:— 

1. That seed-wheat of the greatest density produces 
the densest seed. 

2. The seed-wheat of the greatest density yields the 
greatest amount of dressed corn. 

3. The seed-wheat of medium density generally gives 
the largest number of ears, but the ears are poorer than 
those of the densest seed. 

4. The seed-wheat of medium density generally pro- 
duces the largest number of fruiting plants. 

5. The seed-wheats which sink in water, but float in a 
liquid having the specific gravity 1.247, are of very low 
value, yielding, on an average, but 34.4 lbs. of dressed 
grain for every 100 yielded by the densest seed. 

6. The densest wheat-seeds are the most translucent 
or horny, and contain about one-fourth more proteids 
(or 3 per cent more) than the opake or starchy grains 
from the same kind of wheat, or even from the same 
individual plant, or even from the same ear. 



340 HOW CROPS GROW. 

7. The weight of wheat per bushel depends upon 
many circumstances, and bears no constant relation to 
the density of the seed. 

The densest grains are not, according to Church, 
always the largest. The seeds he experimented with 
ranged from sp. gr. 1.354 to 1.401. 

Marek has shown that specific gravity is no universal 
test of the quality of seed, for while, in case of wheat, 
flax, and colza, the large seeds are generally the denser, 
the reverse is true of horse-beans ( Vicia faba) and peas 
(Vs. St., XIX, 40). 

The Absolute Weight of Seeds from different 
varieties of the same species is known to vary greatly, 
as is well exemplified by comparing the kernels of com- 
mon field maize with those of "pop corn." Similar dif- 
ferences are also observable in different single seeds from 
the same plant, or even from the same pod or ear. Thus, 
Harz obtained what were, to all appearance, normally 
developed seeds that varied in weight as follows : 

from single plants. Milligrams. 

Wheat, Tr it icum vulgare, from l^to 37 

Wheat, Triticum polonicum, «« 21 to 55 

Barley, ffordeum distichon, « 31 to 41 

Oats, Arena sativa, « j9 ^ 30 

Maize, Zea Mays ctnquantino, «< 169 to 201 

Pea, Pisum sativum, <« 143 ^o 502 

FROM SINGLE FRUIT (PODS). 

P r ea ' . . .from 309 to 473 

Vet( J h ' " 33 to 66 

Lu P in > « 486 to 639 

Differences often no less marked are found among the 
seeds in any considerable sample, gathered from a large 
number of plants and representing a crop. Nobbe, with 
great painstaking, has ascertained the average, maxi- 
mum and minimum weights, of 180 kinds of seeds, such 
as are found in commerce or are used in Agriculture, 
Horticulture, and Forestry. The following table gives 
some of his results : 



REPRODUCTIVE ORGANS OF PLANTS. 341 

Absolute Weight of Commercial Seeds. 

Number of Weight of one Seed in 
Samples Milligrams. 
Examined. Average. Maximum. Minimum. 

Oats, 84 28.8 54.1 14.7 

Barley, 66 41.0 48.9 27.7 

Rye, 119 23.3 47.9 13.0 

Wheat 95 37.6 45.8 15.2 

Maize,.' 22 282.7 382.9 114.5 

Beet, 39 22.0 42.4 14.2 

Turnip, Brassica rapifera, . . 23 2.2 3.0 1.4 

Carrot, 35 1.2 1.7 0.8 

Pea, 43 185.8 564.6 46.1 

Kidney Bean, Phaseolus,.... 5 585.6 926.3 367.3 

Horse Bean, Vicia, 7 676.0 2061.0 256.4 

Potato, 3 0.6 0.7 0.5 

Tomato, 5 2.5 2.7 2.4 

Spinage, 4 6.9 9.0 2.4 

Radish, 5 7.1 9.7 5.7 

Lettuce, 18 1.1 1.7 0.8 

Parsnip, 3 3.1 3.8 2.3 

Squash, 5 173.0 322.0 106.7 

Musk Melon, 3 32.9 35.5 28.2 

Cucumber, 6 25.4 27.0 21.0 

Timothy, Phleum pratense,. 73 0.41 0.59 0.34 

Blue Crass, Poa pratensis, . . 28 0.15 0.21 0.10 

Red Clover, 355 1.60 2.08 1.14 

White Clover, 53 0.61 0.69 0.47 

Ten-weeks-stocks, Mattli i- 

ola annua, 4 1.50 1.60 1.39 

Oak, Quevcus pedunculata,. 15 2013.4 4213.5 761.6 

It is noteworthy, that in case of Oats, Eye, Wheat, 
Maize, Beet, Spinage, and Squash, the heaviest seeds 
weigh thrice as much as the lightest. With Turnip, 
Carrot, Kidney-bean, Lettuce, and Blue grass, some 
seeds are double the weight of others. The horse-bean 
gives some seeds eight times as heavy as others. The 
differences brought out in the Table in many cases are 
due to the representation of different varieties ; the 
larger seeds, to some extent, belonging to larger plants ; 
but the great range of weight, noted with regard to the 
seed of the Oak, applies to 15 crops of sound acorns from 
one and the same tree, gathered in 15 successive years. 

In many varieties of Indian Corn, the kernels at the 
base of the ear are larger,, and those at the tip are 
smaller, than those of the middle portion. Other varie- 
ties are characterized by great uniformity in the size of 
the kernels, having been " bred up " to this quality by 
careful seed-selection. 

It is well-known that the middle part of the ears of 



342 HOW CROPS GROW. 

wheat and barley produce the heaviest kernels. Nobbe 
numbered and weighed the spikelets from an ear of six- 
rowed barley and from one of winter wheat. Either ear 
contained 27 spikelets, each with three kernels. The 
kernels of the smallest barley-spikelet, No. 2, from the 
base of the ear, weighed 1.5 milligrams; those of the 
largest, No. 10, weighed 103.5 mg. No. 27 weighed 
32.5 mg. The corresponding numbers in wheat weighed 
0.5, 34.5 and 10.8 mg. 

In case of barley, each of the first five spikelets, count- 
ing from the base, weighed less than 70 milligrams. 
The 6th to the 22d, inclusive, weighed 75 mg. or more. 
The 7th to the 16th weighed 90 mg. or more. The 17th 
to the 21st, 80 mg. or more. Thence, to the tip, the 
weight rapidly declined to about 30 milligrams. 

The wheat kernels exhibited quite similar variation of 
weight. 

Dividing the 27 spikelets into three groups of nine 
each, we have the following comparison of weights of 
seeds, to which is added the total lengths of the rootlets 
that were formed after germination had gone on for five 
days : 

BARLEY. WHEAT. 

Weight. Length of Root. Weight. Length of Root. 
Spikelets, 1 to 9 426 mg. 670 mm. 153 mg. 223 mm. 

10 to 18 828 " 3281 " 282 " 1094 « 

18 to 27 512 " 1364 " 191 " 454 « 

The seeds of the middle portion of the ears of barley and 
wheat are thus seen to be very considerably heavier than 
those of either the base or tip, and also show greater ger- 
minative vigor, as measured by the comparative growth 
of the roots in a given short time. 

The greater weight and germinative energy of the 
seeds from the middle of the ears, stand in relation to 
the fact that these seeds are the oldest— the flowers from 
which they develop being the first to open and fructify. 
In case of a head of summer rye, Nobbe found that the 



REPRODUCTIVE ORGANS OF PLANTS. 343 

33 spikelets, each with two buds, required a iveeJc for 
blossoming; the first of the 66 flowers to open were 
mostly those of the thirties and forties, and the last 
those of the tens, fifties, and sixties, counting from the 
base upward. These middle seeds had accordingly an 
earlier start, and better chance for full development, 
than those at the base and tip of the ear. 

Oat kernels usually grow in pairs, the upper one of 
each pair being in general lighter and smaller than the 
lower one. Nobbe counted out 200 upper kernels, 200 
lower kernels, and 200 average kernels, without selection. 
These were weighed, and, after soaking in water for 24 
hours, were placed in a sprouting apparatus at a tem- 
perature of about 70° F. The results were as follows : 

100 seeds Number of seeds that sprouted, 

weighed. On the Total in 
Grams. 3d, 4th, 5th, 6th, 7th, 8th, 9th, 10th days. 10 days. 

Upper Kernels, 1.53 2 100 76 15 3 2 1 199 

Lower Kernels, 3.46 109 75 9 3 2 198 

Average Kernels, 2.69 45 110 30 8 4 1 1 199 

• 

Here, as in case of wheat and barley, the light seeds 
were slower to germinate. 

In general, it would appear 'that, other things being 
equal, stronger and more perfect plants and larger 
crops are produced from heavy than from small seeds. 
Many comparisons are on record that have given such 
results ; not only small trials in garden plats, but also 
field experiments on a larger scale. 

Lehmann sowed, on each of three plats of 92 square 
feet, the same number (528) of peas, of the same kind 
but of different weight, with results as here tabulated • 

Weights of 100 No. of Yield (grams). 

seed-peas, plants. Kernels. Pods. Straw. Total. 

Small seed-peas, 160 gm. 423 998 280 2010 3288 

Medium seed-peas, 221 " 478 1495 357 2630 4482 

Large seed-peas, 273 " 480 1814 437 3170 5421 

Of the peas sown, there failed to germinate about 9 



344 HOW CROPS GROW. 

per cent, both of the large and medium sizes, and 20 per 
cent of the small ones. 

The total produce from the small seeds was less abun- 
dant in all respects than that of the medium, and this 
less than that of the large seeds. 

Calculated upon the same number of plants, the differ- 
ences, though less in degree, are still very decided : 



100 Plants Yielded 


Kernels. 


Pods. 


Straw. 


Total, 


From small seeds, 


236 


66 


475 


777 


From medium seeds, 


313 


75 


550 


938 


From large seeds, 


378 


91 


660 


1129 



Lehmann, in another experiment, found that from the 
same weight of seed a larger crop is given by large seed 
than by small, although the number of plants may be 
considerably less. 

From the same weight (188 gm.) of seed-peas were 
produced : 

Number of Weight of Kernels 

Seed-peas. Plants. per 92 sq. ft. Per 100 plants. 
By small seed, 780 680 1590 234 

By medium seed, 530 505 2224 440 

By large seed, 384 360 2307 640 

Driesdorff sowed separately, on the same land, winter 
wheat, as winnowed, and .the same divided by sifting into 
three sizes. In April and May the vegetation from the 
largest seed was evidently in advance, and at harvest 
the relative yield for 100 of unsifted seed was 121 from 
the largest, 105 for the medium, and 95 for the smallest 
seed. 

Improved varieties are often the result of continued 
breeding from the heaviest or largest seeds, accompanied 
by high culture on rich soil, and thin planting, so that 
the roots have abundant earth for Unhindered develop- 
ment. 

Hallet, in 1857, selected two ears of Nursery Wheat, 
" the finest quality of red wheat grown in England," con- 
taining, together, 87 grains, and planted the kernels 12 
inches apart every way. At harvest one prime grain 



REPRODUCTIVE ORGANS OF PLANTS. 345 

produced 10 ears, that contained in the aggregate 688 
kernels. The finest 10 ears that could be selected from 
the whole produce' of the other 86 grains yielded but 
598 kernels. The 79 kernels of the one best ear were 
planted as before, and the produce of the finest seed, as 
shown by the harvest, was used for the next year's sow- 
ing. The results of continuing this process of selection 
are tabulated below : 

Number of 

Length, Containing, ears on 

Year. inches. grains. finest stool. 

1857. Original, 4| 47 

1868. Finest ear, 6j 79 jq 

1859. Finest ear, 7| 9^ 22 

1860. Ears imperfect from wet season,... 39 

1861. Finest ear, 8| 123 52 

In five years, accordingly, the length of the ears was 
doubled, their contents nearly trebled, and the tillering 
capacity of the plant increased five-fold. {Journal Royal 
Ag. Soc, XXII, p. 374.) 

Wollny has given account of 27 garden trials, with 
large and small seeds of rye, buckwheat, beans, vetches, 
peas, lupins, soybeans, colza, mustard, maize, and red- 
clover, on plats of four square meters (43 sq. ft.), during 
the years 1873 to 1880, with the nearly invariable results : 
1, that the quantity of crop increases with the size of 
the seed ; 2, that the large seed produces principally 
large seed, and the small seed small ; 3, that the relative 
productiveness of the small seed is greater than that of 
the large ; and 4, that the vitality of the plants from 
small seed is usually less than that of the plants from 
large seed. 

The facts of experience fully justify the conclusion 
that, in general, other things being equal, the heaviest 
seed is the best. 

Signs of Excellence. — So far as the common judg- 
ment can determine by external signs, the best seed is that 
which, on the one hand, is large, plump, and heavy, and on 



346 HOW CROPS GROW. 

the other is fresh or bright to the eye, and free from 
musty odor. The large, plump, and heavy seeds are 
those which have attained the fullest development, and 
can best support the embryo when it shall begin to 
grow ; those fresh in color and odor are likely to be new, 
and to have the most vigorous vitality. 

Ancestry ; Race-Vigor ; Constancy. — There are, 
however, important qualities in seed that are involved in 
their heredity and give no outward token of their pres- 
ence. Kace-vigor and Constancy are qualities of this 
sort, and these wonderfully persist in some kinds of seed 
and are lacking in others. All cultivated plants occur 
in numerous varieties, and, as the years go on, older 
varieties "run out " or are neglected and forgotten, their 
place being taken by newer and often, or for a time, bet- 
ter ones. It would appear that a long course of careful 
cultivation under the most favorable and uniform condi- 
tions, coupled with careful and intelligent selection of 
seed from the best-developed plants, not only leads to 
the formation of the best varieties, but tends to establish 
their permanence, so that when soil, climate, and care 
are unfavorable, the kind maintains its character and 
makes a stout resistance to deteriorating influences. 

In order to properly appreciate the value of seed, its 
Pedigree must therefore be known. But seed of ances- 
try, that has a long-established character for certain 
qualities, in a given locality, may prove of little value 
under widely different circumstances, or, if its products 
be cultivated under new conditions, it may lose its char- 
acteristics more or less, and develop into other varieties. 
It is well known that various perennial plants of tropical 
climates, like the castor bean, become annuals in north- 
ern latitudes, and it may easily happen that the seed of 
some prized variety which is of unquestioned pedigree, as 
far as the remote lines of its descent can indicate, is of lit- 
tle worth in soils or climates to which it is unaccustomed, 



REPRODUCTIVE ORGANS OF PLANTS. 347 

s. 

from not having the power to transmit the specially 
valuable qualities of its progenitors. In high, northern 
latitudes, the summer cereals ripen after a short period 
of rapid growth, but seed of such grain, sown in the soil 
of temperate regions, does not produce early varieties ; its 
rate of growth, after a few years at most, is governed by 
the climate to which it is exposed. In considering the 
pedigree of seed, therefore, it is not merely the repute 
or characters of the ancestry, but the probability that 
the ancestral excellencies reside in and will be trans- 
mitted by the seed, that constitutes the practical point. 



DIVISION III. 

LIFE OF THE PLANT. 

CHAPTER I. 

GERMINATION. 

INTRODUCTORY. 

Having traced the composition of vegetation from its 
ultimate elements to the proximate organic compounds, 
and studied its structure in the simple cell as well as in 
the most highly-developed plant, and, as far as needful, 
explained the characters and functions of its various 
organs, we approach the subject of Vegetable Life 
and Nutrition, and are ready to inquire how the plant 
increases in bulk and weight and produces starch, sugar, 
oil, albuminoids, etc., which constitute directly or in- 
directly almost the entire food of animals. 

The beginning of the agricultural plant is in the 
flower, at the moment of fertilization by the action of a 
pollen tube on the contents of the embryo-sack. Each 
embryo whose development is thus ensured is a plant in 
miniature, or rather an organism that is capable, under 
proper circumstances, of unfolding into a plant. 

349 



350 HOW CROPS GROW. 

The first process of development, wherein the young 
plant commences to manifest its separate life, and in 
which it is shaped into its proper and peculiar form, is 
called germination. 

The General Process and Conditions of Germin- 
ation are familiar to all. In agriculture and ordinary 
gardening we bury the ripe and sound seed a little way 
in the soil, and in a few days, or weeks, it usually sprouts, 
provided it finds a certain degree of warmth and moisture. 

Let us attend somewhat in detail first to the phenom- 
ena of germination and afterward to the requirements of 
the awakening seed. 



2, 



THE PHENOMENA OF GERMINATION. 

The student will do well to watch with care the various 
stages of the act of germination, as exhibited in several 
species of plants. For this purpose a dozen or more 
seeds of each plant are sown, the smaller, one-half, the 
larger, one inch deep, in a box of earth or sawdust, kept 
duly warm and moist, and one or tw r o of each kind are 
uncovered and dissected at successive intervals of 12 
hours until the process is complete. In this way it is 
easy to trace all the visible changes which occur as the 
embryo is quickened. The seeds of the kidney-bean, 
pea, of maize, buckwheat, and barley, may be employed. 

We thus observe that the seed first absorbs a large 
amount of moisture, in consequence of which it swells 
and becomes more soft. We see the germ enlarging be- 
neath the seed coats, shortly the integuments burst and 
the radicle appears, afterward the plumule becomes 
manifest. 

In all agricultural plants the radicle buries itself in 



GERMINATION. 351 

the soil. The plumule ascends into the atmosphere and 
seeks exposure to the direct light of the sun. 

The endosperm, if the seed have one, and in many 
cases the cotyledons (so with the horse-bean, pea, maize, 
and barley), remain in the place where the seed was 
deposited. In other cases (kidney-bean, buckwheat, 
squash, radish, etc.) the cotyledons ascend and become 
the first pair of leaves. 

The ascending plumule shortly unfolds new leaves, 
and, if coming from the seed of a branched plant, lateral 
buds make their appearance. The radicle divides and 
subdivides in beginning the issue of true roots. 

When the plantlet ceases to derive nourishment from 
the mother-seed the process is finished. 



3. 



THE CONDITIONS OF GERMINATION". 

As to the Conditions of Germination we have to con- 
sider in detail the following: : — 

a. Temperature. — Seeds sprout within certain more 
or less narrow limits of warmth. 

Sachs has approximately ascertained, for various agri- 
cultural seeds, the limits of warmth at which germina- 
tion is possible. The lowest temperatures range from 
below 40° to 55°, the highest, from 102° to 116°. Below 
the minimum temperature a seed preserves its vitality, 
above the maximum it is killed. He finds, likewise, that 
the point at which the most rapid germination occurs is 
intermediate between these two extremes, and lies be- 
tween 79° and 93°. Either elevation or reduction of 
temperature from these degrees retards the act of 
sprouting. 

In the following table are given the special tempera- 
tures for six common plants : 



352 HOW CROPS GROW. 





Lowest 


Highest 


Temperature of most 




Temperature. 


Temperature. 


rapid Germination. 


Wheat,* 


40° F. 


104° F. 


84° F. 


Barley, 


41 


104 


84 


Pea, 


44.5 


102 


84 


Maize, 


48 


115 


93 


Scarlet-bean, 


49 


111 


79 


Squash, 


54 


115 


93 



For the agricultural plants cultivated in New England, 
a range of temperature of from 55° to 90° is adapted for 
healthy and speedy germination. 

It will be noticed in the above Table that the seeds of 
plants introduced into northern latitudes from tropical 
regions, as the squash, bean, and maize, require and 
endure higher temperatures than those native to temper- 
ate latitudes, like wheat and barley. The extremes given 
above are by no means so wide as would be found were 
we to experiment with other plants. Some seeds will 
germinate near 32°, the freezing point of water, as is 
true of wheat, rye, and water-cress, as well as of various 
alpine plants that grow in soil wet with the constant 
drip from melting ice. On the other hand, the cocoa- 
nut is said to yield seedlings with greatest certainty when 
the heat of the soil is 120°. 

Sachs has observed that the temperature at which 
germination takes place materially influences the relative 
development of the parts, and thus the form, of the seed- 
ling. Very low temperatures retard the production of 
new rootlets, buds, and leaves. The rootlets which are 
rudimentary in the embryo become, however, very long. 
On the other hand, very high temperatures cause the 
rapid formation of new roots and leaves, even before 
those existing in the germ are fully unfolded. The 
medium and most favorable temperatures bring the 
parts of the embryo first into development, at the same 
time the rudiments of new organs are formed which are 
afterwards to unfold. 



* Wheat, and probably barley, may, occasionally, germinate at, or 
very near, 32°. 



GEKMINATION. 353 

b. Moisture. — A certain amount of moisture is indis- 
pensable to all growth. In germination it is needful 
that the seed should absorb water so that motion of the 
contents of the germ-cells can take place. Until the 
seed is more or less imbued with moisture, no signs of 
sprouting are manifested, and if a half-sprouted seed 
be allowed to dry the process of growth is effectually 
checked. 

The degree of moisture different seeds will endure or 
require is exceedingly various. The seeds of aquatic 
plants naturally germinate when immersed in water. 
The seeds of most agricultural plants, indeed, will 
quicken under water, but they germinate most health- 
fully when moist but not wet. Excess of water often 
causes seeds to rot. 

c. Oxygen Gas. — Free Oxygen, as contained in the 
air, is likewise essential. Saussure demonstrated by ex- 
periment that proper germination is impossible in its 
absence, and cannot proceed in an atmosphere of other 
gases. The chemical activity of oxygen appears to be 
the means of exciting the growth of the embryo. 

d. Light. — It has been erroneously taught that light 
is prejudicial to germination, and that therefore seed 
must be covered. (Johnston's Lectures on Ag. Chem. & 
Geology, 2d Eng. Ed., pp 226 and 227.) Nature does 
not bury seeds, but scatters them on the surface of the 
ground of forest and prairie, where they are, at the most, 
half-covered and by no means removed from the light. 
The warm and moist forests of tropical regions, which, 
though shaded, are by no means dark, are covered with 
sprouting seeds. The seeds of heaths, calceolarias, and 
some other ornamental plants, germinate best when un- 
covered, and the seeds of common agricultural plants 
will sprout when placed on moist sand or sawdust, with 
apparently no less certainty than when buried out of 
sight. 

23 



354 HOW CROPS GROW. 

Finally, R. Hoffmann (Jahresbericht r tiber* Agricultur 
Chem., 1864, p. 110) found, in special experiments with 
24 kinds of agricultural seeds, that light exercises no 
appreciable influence of any kind on germination. 

The time required for Germination varies exceed- 
ingly according to the kind of seed. It is said that the 
fresh seeds of the willow begin to sprout within 12 hours 
after falling to the ground. Those of clover, wheat, and 
other grains, mostly germinate in three to ten days. 
The fruits of the walnut, pine, and larch lie four to six 
weeks. before sprouting, while those of some species of 
ash, beech, and maple are said not to germinate before 
the expiration of one and a half or two years. 

The starchy and thin-skinned seeds quicken most 
readily. The oily seeds are in general more sIoav, while 
such as are situated within thick and horny or other- 
wise resistant envelopes require the longest periods to 
excite growth. 

The time necessary for germination depends naturally 
upon the favorableness of other conditions. Cold and 
drought delay the process, when they do not check it 
altogether. Seeds that are buried deeply in the soil may 
remain for years, preserving, but not manifesting, their 
vitality, because they are either too dry, too cold, or 
have not sufficient access to oxygen to set the germ in 
action. 

Notice has already been made of the frequent presence 
in clover-seed, for example, of a small proportion of 
seeds that have a dense coat which prevents imbibition 
of water and delays their germination for long periods. 
See p. 335. 

To speak with precision, we should distinguish the 
time from planting the dry seed to the commencement 
of germination, which is marked by the rootlet becom- 
ing visible, and the period that elapses until the process 
is complete ; i. e., until the stores of the mother-seed are 



GERMINATION. 355 

exhausted, and the young plant is wholly cast upon its 
own resources. 

At 41° F., in the experiments of Haberlandt, the root- 
let issued after four days, in the case of rye, and in five 
to seven days in that of the other grains and clover. 
The sugar-beet, however, lay at this temperature 22 days 
before beginning to sprout. 

At 51°, the time was shortened about one-half in case 
of the seeds just mentioned. Maize required 11, kidney- 
beans 8, and tobacco 31 days at this temperature. 

At 65° the cereals, clover, peas, and flax began to 
sprout in one to two days ; maize, beans, and sugar-beet 
in three days, and tobacco in six days. 

The time of completion varies with the temperature 
much more than that of beginning. It is, for example, 
according to Sachs, 

at 41—55° for wheat and barley 40 — 45 days, 
at 95— 100° " " 10—12 " 

At a given temperature small seeds complete germina- 
tion much sooner than large ones. Thus at 55-60° the 
process is finished 

with beans in 30 — 40 days. 
" maize in 30—35 " 
44 wheat in 20—25 u 
44 clover in 8 — 10 44 

These differences are simply due to the fact that the 
smaller seeds have smaller stores of nutriment for the 
young plant, and are therefore more quickly exhausted. 

Proper Depth of Sowing. — The soil is usually the 
medium of moisture, warmth, etc., to the seed, and it 
affects germination only as it influences the supply of 
these agencies ; it is not otherwise essential to the pro- 
cess. The burying of seeds, when sown in the field or 
garden, serves to cover them away from birds and keep 
them from drying up. In the forest, at spring-time, we 
may see innumerable seeds sprouting upon the surface, 
or but half covered with decayed leaves. 



356 HOW CROPS GROW. 

While it is the nearly universal result of experience in 
temperate regions that agricultural seeds germinate most 
surely when sown at a depth not exceeding one or two 
inches, there are circumstances under which a widely 
different practice is admissible or even essential. In the 
light and porous soil of the gardens of New Haven, peas 
may be sown six to eight inches deep without detriment, 
and are thereby better secured from the ravages of the 
domestic pigeon. 

The Moqui Indians, dwelling upon the table lands of 
the higher Colorado, deposit the seeds of maize 12 or 14 
inches below the surface. Thus sown, the plant thrives, 
while, if treated according to the plan usual in the 
United States and Europe, it might never appear above 
ground. The reasons for such a procedure are the fol- 
lowing : The country is without rain and almost with- 
out dew. In summer the sandy soil is continuously 
parched by the sun, at a temperature often exceeding 
100° in the shade. It is only at the depth of a foot or 
more that the seed finds the moisture needful for its 
growth — moisture furnished by the melting of the winter 
snows.* 

R. Hoffmann, experimenting in a light, loamy sand, 
upon 24 kinds of agricultural and market-garden seeds, 
found that all perished when buried 12 inches. When 
planted 10 inches deep, peas, vetches, beans, and maize, 
alone came up ; at 8 inches there appeared, besides the 
above, wheat, millet, oats, barley, and colza ; at 6 inches, 
those already mentioned, together with winter colza, 
buckwheat, and sugar-beets ; at 4 inches of depth the 
above and mustard, red and white clover, flax, horse- 
radish, hemp, and turnips ; finally, at 3 inches, lucern 
also appeared. Hoffmann states that the deep-planted 
seeds generally sprouted most quickly, and all early dif- 

* For these interesting facts, the writer is indebted to Prof. J. S. 
Newberry. 



GERMINATION. 357 

ferences in development disappeared before the plants 
blossomed. 

On the other hand, Grouven, in trials with sugar-beet 
seed— made, most probably, in a well-manured and rather 
heavy soil— found that sowing at a depth of three-eighths 
to one and a fourth inches gave the earliest and strongest 
plants ; seeds deposited at a depth of two and a half 
inches required five days longer to come up than those 
planted at three-eighths of an inch. It was further shown 
that seeds sown shallow, in a fine wet clay, required four 
to five days longer to come up than those placed at the 
same depth in the ordinary soil. 

•Not only the character of the soil, which influences the 
supply of air and warmth, but the kind of weather 
which determines both temperature and degree of moist- 
ure, have their effect upon the time of germination, and 
since these conditions are so variable, the rules of prac- 
tice are laid clown, and must be received, with a certain 
latitude. 

§ 4 - 

THE CHEMICAL PHYSIOLOGY OF GERMINATION. 

The Nutrition of the Seedling.— The young 
plant grows at first exclusively at the expense of the 
seed. It may be aptly compared to the suckling animal, 
which, when new-born, is incapable of providing its 
own nourishment, but depends upon the milk of its 
mother. 

The Nutrition of the Seedling falls into three pro- 
cesses, which, though distinct in character, proceed sim- 
ultaneously. These are : 1, Solution of the Nutritive 
Matters of the Cotyledons or Endosperm ; 2, Transfer ; 
and 3, Assimilation of the same. 

1. The Act of Solution has no difficulty in case of 



358 HOW CROPS GROW. 

dextrin, gum, the sugars, and soluble proteids. The 
water which the seed imbibes, to the extent of one-fourth 
to five-fourths of its weight, at once dissolves them. 

It is otherwise with the fats or oils, with starch and 
with proteids, which, as such, are nearly or altogether 
insoluble in water. In the act of germination provision 
is made for transforming these bodies into the soluble 
ones above mentioned. So far as these changes have 
been traced, they are as follows : 

Solution of Fats. — Sachs was the first to show that 
squash-seeds, which, when ripe, contain no starch, 
sugar, or dextrin, but are very rich in oil (50%) and 
albuminoids (40%), suffer by germination such chemical 
change that the oil rapidly diminishes in quantity (nine- 
tenths disappear), while, at the same time, starch, and 
in some cases sugar, is formed. (Vs. St., Ill, p. 1.) 

Solution of Starch. — The starch that is thus organized 
from the fat of the oily seeds, or that which exists 
ready-formed in the farinaceous (floury) seeds, undergoes 
further changes, which have been previously alluded to 
(p. 50), whereby it is converted into substances that are 
soluble in water, viz., dextrin and dextrose. 

Solution of Albuminoids. — Finally, the insoluble al- 
buminoids are gradually transformed into soluble modi- 
fications. 

Chemistry of Malt. — The preparation and proper- 
ties of malt may serve to give an insight into the nature 
of the chemical metamorphoses that have just been 
indicated. 

The preparation is in this wise. Barley or wheat 
(sometimes rye) is soaked in water until the kernels are 
soft to the fingers ; then it is drained and thrown up in 
heaps. The masses of soaked grain shortly dry, become 
heated, and in a few days the embryos send forth their 
radicles. The heaps are shoveled over, and spread out 
so as to avoid too great a rise of temperature, and when 



GERMINATION. 350 

the sprouts are about half an inch in length, the germin- 
ation is checked by drying. The dry mass, after remov- 
ing the sprouts (radicles), is malt, such as is used in the 
manufacture of beer. 

Malt thus consists of starchy seeds, whose germination 
has been checked while in its early stages. The only 
product of the beginning growth— the sprouts— being 
removed, it exhibits in the residual seed the first results 
of the process of solution. 

The following figures, derived from the researches of 
Stein, in Dresden ( Wilda's Centralblatt, 1860, 2, pp. 8- 
23), exhibit the composition of 100 parts of Barley, and 
of the 92 parts of Malt, and the two and a half of Sprouts 
which 100 parts of Barley yield.* 

- 100 pts. of 1 (92pts. of ) , < 1\ of ), 

Composition of Barley. J — f Malt. ) + 1 Sprouts. \ + 

\ sn 2.42 2.11 0.29 

Starch, 54.48 47.43 

Fat 3.56 2.09 0.08 

Insoluble Albuminoids 11.02 9.02 0.37 

Soluble Albuminoids, 1.26 1.96 0.40 

Dextrin, t U.50 6.95) 

Extractive Matters (soluble in 0.47 

water and destitute of nitrogen) 0.90 3.68) 

Cellulose 19.86 18.76 0%89 

100. 92. 2.5 

It is seen from the above statement that starch, fat, 
and insoluble albuminoids have diminished in the malt- 
ing process ; while soluble albuminoids, dextrin, and 
other soluble non-nitrogenous matters have somewhat 
increased in quantity. With exception of 3% of soluble 
"extractive matters," J the differences in composition 
between barley and malt are not striking. 

* The analyses refer to the materials in the dry state. Ordinarily 
they contain" from 10 to 16 per cent of water. It must not be omitted to 
mention that the proportions of malt and sprouts, as well as their 
composition, vary somewhat according to circumstances ; and further- 
more, the best analyses which it is possible to make are but approxi- 
mate. ^ , A . . ^ 1 X- 

t Later investigators deny the existence of dextrin in barley, but 
find, instead, amidulin and amylan. See p. 62, note. 

% The term extractive matters is here applied to soluble substances, 
whose precise nature is not understood. They constitute a mixture 
which the chemist is not able to analyze. 



360 HOW CROPS GROW. 

The properties of the two are, however, remarkably 
different. If malt be pulverized and stirred in warm 
water (155° F.) for an hour or two, the whole of the 
starch disappears, while sugar and dextrin take its place. 
The former is recognized by the sweet taste of the wort, 
as the solution is called. On heating the wort to boiling, 
a little albuminoid is coagulated, and may be separ- 
ated by filtering. This comes in part from the trans- 
formation of the insoluble albuminoids of the barley. 
On adding to the filtered liquid its own bulk of alcohol, 
dextrin becomes evident, being precipitated as a white 
powder. 

Furthermore, if we mix two to three parts of starch 
with one of malt, we find that the whole undergoes the 
same change. An additional quantity of starch remains 
unaltered. 

The process of germination thus develops in the seed 
an agency by which the conversion of starch into soluble 
carbhydrates is accomplished with great rajDidity. 

Diastase. — Payen & Persoz attributed this action to 
the nitrogenous ferment which they termed Diastase, 
and which is found in the germinating seed in the vicin- 
ity of the embryo, but not in the radicles. They assert 
that one part of diastase is capable of transforming 2,000 
parts of starch, first into dextrin and finally into sugar, 
and that malt yields one five-hundredth of its weight of 
this substance. See p. 103. 

A short time previous to the investigations of Payen 
& Persoz (1833), Saussure found that Mucedin,* the 
soluble nitrogenous body wdiich may be extracted from 
gluten (p. 92, note), transforms starch in the manner 
above described, and it is now known that various albu- 
minoids may produce the same effect, although the rap- 



* Saussure designated this body mucin, hut this term being established 
as the name of the characteristic ingredient of animal mucus, Ritthau- 
sen has replaced it by mucedin. 



GERMINATION. 



361 



idity of the action and the amount of effect are usually 
far less than that exhibited by the so-called diastase. 

It must not be forgotten, however, that in all cases in 
which the conversion of starch into dextrin and sugar is 
accomplished artificially, an elevated temperature is re- 
quired, whereas, in the natural process, as shown in the 
germinating seed, the change goes on at ordinary or even 
low temperatures. 

It is generally taught that ox3 T gen, acting on the albu- 
minoids in presence of water, and within a certain range 
of temperature, induces the decomposition which confers 
on them the power in question. 

The necessity for oxygen in the act of germination has 
been thus accounted for, as needful to the solution of 
the starch, etc., of the cotyledons. 

This may be true at first, but, as we shall presently see, 
the chief action of oxygen is probably of another kind. 

How diastase or other similar substances accomplish 
the change in question is not certainly known. 

Soluble Starch. — The conversion of starch into 
sugar and dextrin is thus in a sense explained. This is 

not, however, the only change 
of which starch is suscepti- 
ble. In the bean (Phaseol- 
us multifiorus) Sachs (Sitz- 
ungsberichte der Wi ener 
Akad., XXXVII, 57) in- 
forms us that the starch of 
the cotyledons is dissolved, 
passes into the seedling, and 
reappears (in part, at least) 
as starch, without conver- 
sion into dextrin or sugar, 
as these substances do not appear in the cotyledons during 
any period of germination, except in small quantity near 
the joining of the seedling. Compare p. 52, Amidulin. 




Fig. 65. 



362 HOW CHOPS GROW. 

The same authority gives the following account of the 
microscopic changes observed in the starch-grains them- 
selves, as they undergo solution. The starch-grains of 
the bean have a narrow interior cavity (as seen in Fig. 
65, 1). This at first becomes filled with a liquid. 
Next, the cavity appears enlarged (2), its borders assume 
a corroded appearance (3, 4), and frequently channels 
are seen extending to the surface (4, 5, 6). Finally, the 
cavity becomes so large, and the channels so extended, 
that the starch-grain falls to pieces (7, 8). Solution 
continues on the fragments until they have completely 
disappeared. 

Soluble Albuminoids. — The insoluble proteids of 
the seed are gradually transferred to the young plant, 
.probably by ferment-actions similar to those referred 
to under the heading " Proteoses and Peptones," p. 100. 

The production of small quantities of acetic and lactic 
acids (the acids of vinegar and of sour milk) has been 
observed in germination. These acids perhaps assist in 
the solution of the albuminoids. 

Gaseous Products of Germination. — Before leav- 
ing this part of our subject, it is proper to notice some 
other results of germination which have been thought to 
belong to the process of solution. On referring to the 
table of the composition of malt, we find that 100 parts 
of dry barley yield 92 parts of malt and 2£ of sprouts, 
leaving 5£ parts unaccounted for. In the malting pro- 
cess, 1J parts of the grain are dissolved in the water in 
which it is soaked. The remaining 4 parts escape into 
the atmosphere in the gaseous form. 

Of the elements that assume the gaseous condition, 
carbon does so to the greatest extent. It unites with 
atmospheric oxygen (partly with the oxygen of the 
seed, according to Oudemans), producing carbonic acid 
gas (C0 2 ). Hydrogen is likewise separated, partly in 
union with oxygen, as water (H 2 0), but to some degree 



GERMINATION. 363 

in the free state. Free nitrogen appears in considerable 
amount (Schulz, Jour, fur Prakt. Chem., 87, p. 163), 
while very minute quantities of Hydrogen and of Nitro- 
gen combine to gaseous ammonia (NH 3 ). 

Heat developed in Germination. — These chemical 
changes, like all processes of oxidation, are accompanied 
with the production of heat. The elevation of temper- ' 
ature may be imperceptible in the germiuation of a sin- 
gle seed, but the heaps of sprouting grain seen in the 
malt-house, warm so rapidly and to such an extent that 
much care is requisite to regulate the process ; otherwise 
the malt is damaged by over-heating. 

2. The Transfer of the Nutriment of the Seed- 
ling from the cotyledons or endosperm where it has un- 
dergone solution, takes place through the medium of the 
water which the seed absorbs so largely at first. This 
water fills the cells' of the seed, and, dissolving their con- 
tents, carries them into the young plant as rapidly as 
they are required. The path of their transfer lies thrgugh 
the point where the embryo is attached to the cotyle- 
dons ; thence they are distributed at first chiefly down- 
wards into the extending radicles, after a little while 
both downwards and upwards toward the extremities of 
the seedling. 

Sachs has observed that the carbhydrates (sugar and 
dextrin) occupy the cellular tissue of the rind and pith, 
which are penetrated by numerous air-passages ; while 
at first the albuminoids chiefly diffuse themselves through 
the intermediate cambial tissue, which is destitute of 
air-passages, and are present in largest relative quantity 
at the extreme ends of the rootlets and of the plumule. 

In another chapter we shall notice at length the phe- 
nomena and physical laws which govern the diffusion of 
liquids into each other and through membranes similar 
to those which constitute the walls of the cells of plants, 
and there shall be able to gather some idea of the causes 



3G4 HOW CROPS GROW. 

which set up and maintain the transfer of the materials 
of the seed into the infant plant. 

3. Assimilation is the conversion of the transferred 
nutriment into the substance of. the plant itself. This 
process involves two stages, the first being a chemical, 
the second, a structural transformation. 

The chemical changes in the embryo are, in part, 
simply the reverse of those which occur in the cotyle- 
dons ; viz., the soluble and structureless proximate prin- 
ciples are metamorphosed into the insoluble and organ- 
ized ones of the same or similar chemical composition. 
Thus, dextrin may pass into cellulose, and the soluble 
albuminoids may revert in part to the insoluble condi- 
tion in which they existed in the ripe seed. 

But many other and more intricate changes proceed in 
the act of assimilation. With regard to a few of these 
we have some imperfect knowledge. 

Dr. Sachs informs us that when the embryo begins to 
grow, its expansion at first consists in the enlargement 
of the ready-formed cells. As a part elongates, the 
starch which it contains (or which is formed in the early 
stages of this extension) disappears, and sugar is found 
in its stead,' dissolved in the juices of the cells. When 
the organ has attained its full size, sugar can no longer 
be detected ; while the walls of the cells are found to 
have grown both in circumference and thickness, thus 
indicating the accumulation of cellulose. 

Oxygen Gas needful to Assimilation. — Traube 
has made some experiments, which prove conclusively 
that the process of assimilation requires free oxygen to 
surround and to be absorbed by the growing parts of the 
germ. This observer found that newly-sprouted pea- 
seedlings continued to develop in a normal manner when 
the cotyledons, radicles, and lower part of the stem 
were withdrawn from the influence of oxygen by coat- 
ing with varnish or oil. On the other hand, when the 



GERMINATION. 365 

tip of the plumule, for the length of about an inch, was 
coated with oil thickened with chalk, or when by any 
means this part of the plant was withdrawn from contact 
with free oxygen, the seedling ceased to grow, withered, 
and shortly perished. Traube observed the elongation 
of the stem by the following expedient. 

A young pea-plant was fastened by the cotyledons to a 
rod, and the stem and rod were both graduated by deli- 
cate cross-lines, laid on at equal intervals, by means of a 
brush dipped in a mixture of oil and indigo. The 
growth of the stem was now manifest by the widening of 
the spaces between the lines ; and, by comparison with 
those on the rod, Traube remarked that no growth took 
place at a distance of more than ten to twelve lines from 
the base of the terminal bud. 

Here, then, is a coincidence which appears to demon- 
strate that free oxygen must have access to a growing 
part. The fact is further shown by varnishing one side 
of the stem of a young pea. The varnished side ceases 
to extend, the uncoated portion continues enlarging, 
which results in a curvature of the stem. 

Traube further indicates in what manner the elabora- 
tion of cellulose from sugar may require the co-operation 
of oxygen and evolution of carbon dioxide, as expressed 
by the subjoined equation. 

Glucose. Oxvsen. Carbon dioxide. Water. Cellulose. 

2 (C 12 H 24 12 ) + 24 O = 12 (C0 2 ) + * 4 ( H »°) + Ci2 H 2o0 10 . 

When the act of germination is finished, which occurs 
as soon as the cotyledons and endosperm are exhausted 
of all their soluble matters, the plant begins a fully inde- 
pendent life. Previously, however, to being thus thrown 
upon its own resources, it has developed all the organs 
needful to collect its food from without ; it has unfolded 
its perfect leaves into the atmosphere, and pervaded a 
portion of soil with its rootlets. 



366 HOW CEOPS GROW. 

During the latter stages of germination it gathers its 
nutriment both from the parent seed and from the exter- 
nal sources which afterward serve exclusively for its 
support. 

Being fully provided with the apparatus of nutrition, 
its development suffers no check from the exhaustion of 
the mother seed, unless it has germinated in a sterile 
soil, or under other conditions adverse to vegetative life. 



CHAPTER II. 

THE FOOD OF THE PLANT WHEN INDEPENDENT OF THE 

SEED. 

This subject will be sketched in this place in but the 
briefest outlines. To present it fully would necessitate 
entering into a detailed consideration of the Atmosphere 
and of the Soil, whose relations to the Plant, those of the 
soil especially, are very numerous and complicated. A 
separate volume is therefore required for the adequate 
treatment of these topics. 

The Roots of a plant, which are in intimate contact 
with the soil, absorb thence the water that fills the active 
cells ; they also imbibe such salts as the water of the soil 
holds in solution ; they likewise act directly on the soil, 
and dissolve substances, which are thus first made of 
avail to them. The compounds that the plant must 
derive from the soil are those which are found in its ash, 
since these are not volatile, and cannot, therefore, exist 
in the atmosphere. The root, however, commonly takes 



FOOD AFTEK GERMIXATIOX. 367 

up some other elements of its nutrition to which it has 
immediate access. Leaving out of view, for the present, 
those matters which, though found in the plant, appear 
to be unessential to its growth, viz., silica and sodium 
salts, the roots absorb the following substances, viz. : 



Sulphates 
Phosphates 
Nitrates and 
Chlorides 



Potassium, 
Calcium, 
Magnesium and 
Iron. 



These salts enter the plant by the absorbent surfaces 
of the younger rootlets, and pass upwards, through the 
stem, to the leaves and to the new-forming buds. 

The Leaves, which are unfolded to the air, gather 
from it Carbon dioxide Gas. This compound suffers 
decomposition in the plant ; its Carton remains there, 
its Oxygen or an equivalent quantity, very nearly, is 
thrown off into the air again. 

The decomposition of carbon dioxide takes place only 
by day and under the influence of the sun's light. 

From the carbon thus acquired and the elements of 
water with the co-operation of the ash-ingredients, the 
plant organizes the Carbhydrates. Probably some of the 
glucoses are the first products of this synthesis. Starch, 
in the form of granules, is the first product that is 
recognizable by help of the microscope. 

The formation of carbhydrates appears to proceed in 
the chlorophyl-cells of the leaf, where starch-granules 
first make their appearance. 

The Albuminoids require for their production the 
presence of a compound of Nitrogen. The salts of 
Nitric Acid (nitrates) are commonly the chief, and may 
be the only, supply of this element. 

The other proximate principles, the fats, the alkaloids, 
and the acids, are built up from the same food-elements. 
In most cases the steps in the construction of organic 
matters are unknown to us, or subjects of uncertain con- 
jecture. 



368 HOW CROPS GROW. 

The carbhydrates, albuminoids, etc., that are organ- 
ized in the foliage, are not only transformed into the 
solid tissues of the leaf, but descend and diffuse to every 
active organ of the plant. 

The plant has, within certain limits* a power of select- 
ting its food. The sea-weed, as has been remarked, 
contains more potash than soda, although the latter is 
30 times more abundant than the former in the water of 
the ocean. Vegetation cannot, however, entirely shut 
out either excess of nutritive matters or bodies that are 
of no use or even poisonous to it. 

The functions of the Atmosphere are essentially the . 
same towards plants, whether growing under the con- 
ditions of water-culture or under those of agriculture. 

The Soil, on the other hand, has offices which are pe- 
culiar to itself. We have seen that the roots of a plant 
have the power to decompose salts, e. g., potassium 
nitrate and ammonium chloride (p. 184), in order to 
appropriate one of their ingredients, the other being 
rejected. In water-culture, the experimenter must have 
a care to remove the substance which would thus accu- 
mulate to the detriment of the plant. In agriculture, 
the soil, by virtue of its chemical and physical qualities, 
commonly renders such rejected matters comparatively 
insoluble, and therefore innocuous. 

The Atmosphere is nearly invariable in its composi- 
tion at all times and over all parts of the earth's surface. 
Its power of directly feeding crops has, therefore, a nat- 
ural limit, which cannot be increased by art. 

The Soil, on the other hand, is very variable in com- 
position and quality, and may be enriched and improved, 
or deteriorated and exhausted. 

From the Atmosphere the crop can derive no appreci- 
able quantity of those elements that are found in its 
Ash. 

In the Soil, however, from the waste of both plants 



MOTION OF THE JUICES. oOy 

and animals, may accumulate large supplies of all the 
elements of the Volatile part of Plants. Carbon, cer- 
tainly in the form of carbon dioxide, probably or possi- 
bly in the condition of Humus (Vegetable Mold, Swamp 
Muck), may thug be put as food, at the disposition 
of the plant. Nitrogen is chiefly furnished to crops by 
the soil. Nitrates are formed in the latter from various 
sources, and ammonia-salts, together with certain proxi- 
mate animal principles, viz., urea, guanin, tyrosin, uric 
acid and hippuric acid, likewise serve to supply nitrogen 
to vegetation and are often ingredients of the best ma- 
nures. It is, too, from the soil that the crop gathers all 
the Water it requires, which not only serves as the fluid 
medium of its chemical and structural metamorphoses, 
but likewise must be regarded as the material from which 
it mostly appropriates the Hydrogen and Oxygen of its 
solid components. 



2. 



THE JUICES OF THE PLANT, THEIR NATURE AND 

MOVEMENTS. 

Very erroneous notions have been entertained with 
regard to the nature and motion of sap. It was formerly 
taught that there are two regular and opposite currents 
of sap circulating in the plant. It was stated that the 
"crude sap" is taken up from the soil by the roots, 
ascends through the vessels (ducts) of the wood, to the 
leaves, there is concentrated by evaporation, "elabor- 
ated" by the processes that go on in the foliage, and 
thence descends through the vessels of the inner bark, 
nourishing these tissues in its way down. The facts 
from which this theory of the sap naturally arose admit 
of a very different interpretation ; while numerous con- 
24 



370 HOW CROPS GROW. 

siderations demonstrate the essential falsity of the theory 
itself. 

Flow of Sap in the Plant — not Constant or 
Necessary. — We speak of the Flow of Sap as if a rapid 
current were incessantly streaming through the plant, 
as the blood circulates in the arteries and veins of an ani- 
mal. This is an erroneous conception. . 

A maple in early March, without foliage, with its 
whole stem enveloped in a nearly impervious bark, its 
buds wrapped up in horny scales, and its roots sur- 
rounded by cold or frozen soil, cannot be supposed to have 
its sap in motion. Its juices must be nearly or abso- 
lutely at rest, and when sap runs copiously from an ori- 
fice made in the trunk, it is simply because the tissues 
are charged with water under pressure, which escapes at 
any outlet that may be opened for it. The sap is at rest 
until motion is caused by a perforation of the bark and 
new wood. So, too, when a plant in early leaf is situa- 
ted in an atmosphere charged with moisture, as happens 
on a rainy day, there is little motion of its sap, although, 
if wounded, motion may be established, and water may 
stream more or less from all parts of the plant towards 
the cut. 

Sap does move in the plant when evaporation of water 
goes on from the surface of the foliage. This always 
happens whenever the air is not saturated with vapor. 
When a wet cloth hung out, dries rapidly by giving up 
its moisture to the air, then the leaves of plants lose 
their water more or less readily, according to the nature 
of the foliage. 

Mr. Lawes found that in the moist climate of England 
common plants (Wheat, Barley, Beans. Peas, and Clover) 
exhaled, during five months of growth, more than 200 
times their (dry) weight of water. Hellriegel, in the 
drier climate of Dahme, Prussia, observed exhalation to 
average 300 times the dry weight of various common 



MOTION OF THE JUICES. 371 

crops (p. 312). The water that thus evaporates from the 
leaves is supplied by tl^e soil, and, entering the roots, 
more or less rapidly streams upwards through the stem as 
long as a waste is to be supplied, but this flow ceases 
when evaporation from the foliage is suppressed. 

The upward motion of sap is therefore to a great de- 
great independent of the vital processes, and compara- 
tively unessential to the welfare of the plant. 

Flow of Sap from the Plant; " Bleeding."— It 
is a familiar fact, that from a maple tree " tapped." in 
spring-time, or from a grape-vine wounded at the same 
season, a copious flow of sap takes place, which continues 
for a number of weeks. The escape of liquid from the 
vine is commonly termed " bleeding," and while this 
rapid issue of sap is thus strikingly exhibited in compar- 
atively few cases, bleeding appears to be a universal phe- 
nomenon, one that may occur, at least, to some degree, 
under certain conditions with very many plants. 

The conditions under which sap flows are various, 
according to the character of the plant. Our perennial 
trees have their annual period of active growth in the 
warm season, and their vegetative functions are nearly 
suppressed during cold weather. As spring approaches 
the tree renews its growth, and the first evidence of 
change within is furnished by its bleeding when an open- 
ing is made through the bark into the young wood. A 
maple, tapped for making sugar, loses nothing until the 
spring warmth attains a certain intensity, and then sap 
begins to flow from the wounds in its trunk. The flow 
is not constant, but fluctuates with the thermometer, 
being more copious when the weather is warm, and fall- 
ing off or suffering check altogether as it is colder. 

The stem of the living maple is always charged with 
water, and never more so than in winter.* This water 



* Experiments made in Tharand. Saxony, under direction of Stoeck- 
hardt, show that the proportion of water, both in the bark and wood 



372 HOW CROPS GROW. 

is either pumped into the plant, so to speak, by the root- 
power already noticed (p. 26J|), or it is generated in 
the trunk itself. The water contained in the stem in 
winter is undoubtedly that raised from the soil in the 
autumn. That which first flows from an auger-hole, in 
March, may be simply what was thus stored in the truck ; 
but, as the escape of sap goes on for 14 to 20 days at the 
rate of several gallons per day from a single tree, new 
quantities of water must be continually supplied. That 
these are pumped in from the root is, at first thought, 
difficult to understand, because, as we have seen (p. 272), 
the root-power is suspended by a certain low tempera- 
ture (unknown in case of the maple), and the flow of 
sap often begins when the ground is covered with one or 
two feet of snow, and when we cannot suppose the soil 
to have a higher temperature than it had during the pre- 
vious winter months. Nevertheless, it must be that the 
deeper roots are warm enough to be active all the winter 
through, and that they begin their action as soon as the 
trunk acquires a temperature sufficiently high to admit 
the movement of water in it. That water may be pro- 
duced in the trunk itself to a slight extent is by no 
means impossible, for chemical changes go on there in 
spring-time with much rapidity, whereby the sugar of 
the sap is formed. These changes have not been suffi- 
ciently investigated, however, to prove or disprove the 
generation of water, and we must, in any case, assume 
that it is the root-power which chiefly maintains a pres- 
sure of liquid in the tree. 

The issue of sap from the maple tree in the sugar- 
season is closely connected with the changes of tempera- 
ture that take place above ground. The sap begins to 

of trees, varies considerably in different seasons of the year, ranging, 
in case of the beech, from 35 to 49 per cent of the fresh-felled tree. The 
greatest proportion of water in the wood was found in the months of 
December and January ; in the bark, in March to May. The minimum 
of water in the wood occurred in May, June, and July ; in the bark, 
much irregularity was observed. Chem. Ackersmann, 1866, p. 159. 



MOTION OF THE JUICES. 373 

flow from a cut when the trunk itself is warmed to a cer- 
tain point and, in general, the flow appears to be the 
more rapid the warmer the trunk. During warm, clear 
days, the radiant heat of the sun is absorbed by the dark, 
rough surface of the tree most abundantly ; then the 
temperature of the latter rises most speedily and acquires 
the greatest elevation — even surpasses that of the atmos- 
phere by several degrees ; then, too, the yield of sap is 
most copious. On clear nights, cooling of the tree takes 
place with corresponding rapidity ; then the snow or 
surface of the ground is frozen, and the flow of sap is 
checked altogether. From trees that have a sunny ex- 
posure, sap runs earlier and faster than from those hav- 
ing a cold northern aspect. Sap starts sooner 'from the 
spiles on the south side of a tree than from those towards 
the north. 

^Duchartre (Comptes Rendus, IX, 754) passed a vine 
situated in a grapery, out of doors, and back again, 
through holes, so that a middle portion of the stem was 
exposed to a steady winter temperature ranging from 18° 
to 10° F., while the remainder of the vine, in the house, 
was surrounded by an atmosphere of 70° F. Under 
these circumstances the buds within developed vigor- 
ously, but those without remained dormant and opened 
not a day sooner than buds upon an adjacent vine whose 
stem was all out of doors. That sap passed through the 
cold part of the stem was shown by the fact that the 
interior shoots sometimes wilted, but again recovered 
their turgor, which could only happen from the partial 
suppression and renewal of a supply of water through the 
stem. Payen examined the wood of the vine at the con- 
clusion of the experiment, and found the starch which it 
originally contained to have been equally removed from 
the warm and the exposed parts. 

That the rate at which sap passed through the stem 
was influenced by its temperature is a plain deduction 



374 HOW CROPS GROW. 

from the fact that the leaves within were found wilted 
in the morning, while they recovered toward noon, al- 
though the temperature of the air without remained 
below freezing. The wilting was no doubt chiefly due 
to the diminished power of the stem to transmit water ; 
the return of the leaves to their normal condition was 
probably the consequence of the warming of the stem by 
the sun's radiant heat.* 

One mode in which changes of temperature in the 
trunk influence the flow of sap is very obvious. The 
wood-cells contain, not only water, but air. Both are 
expanded by heat, and both contract by cold. Air, 
especially, undergoes a decided change of bulk in this 
way. Water expands nearly one-twentieth in being 
warmed from 32° to 212°, and air increases in volume 
more than one-third by the same change of temperature. 
When, therefore, the trunk of a tree is warmed by the 
sun's heat, the air is expanded, exerts a pressure on the 
sap, and forces it out of any wound made through the 
bark and wood-cells. It only requires a rise of tempera- 
ture to the extent of a few degrees to occasion from this 
cause alone a considerable flow of sap from a large tree. 
(Hartig. ) 

If we admit that water continuously enters the deep- 
lying roots whose temperature and absorbent power must 
remain, for the most part, invariable from day to day, 
we should have a constant slow escape of sap from the 
trunk were the temperature of the latter uniform and 
sufficiently high. This really happens at times during 
every sugar-season. When the trunk is cooled down to 
the freezing point, or near it, the contraction of air and 
water in the tree makes a vacuum there, sap ceases to 
flow, and air is sucked in through the spile ; as the trunk 



* The temperature of the air is not always a sure indication of that 
of the solid bodies which it surrounds. A thermometer will often rise 
by exposure of the bulb to the direct rays of the sun, 30 or 40° above its 
indications when in the shade. 



MOTION or THE JUICES. 375 

becomes heated again, the gaseous and liquid contents of 
the ducts expand, the flow of sap is renewed, and pro- 
ceeds with increased rapidity until the internal pressure 
passes its maximum. 

As the season advances and the soil becomes heated, 
the root-power undoubtedly acts with increased vigor 
and larger quantities of water are forced into the trunk, 
but at a certain time the escape of sap from a wound 
suddenly ceases. At this period a new phenomenon 
supervenes. The buds which were formed the previous 
summer begin to expand as the vessels are distended with 
sap, and finally, when the temperature attains the proper 
range, they unfold into leaves. At this point we have 
a proper motion of sap in the tree, whereas before there 
was little motion at all in the sound trunk, and in the 
tapped stem the motion was towards the orifice and 
thence out of the tree. 

The cessation of flow from a cut results from two cir- 
cumstances : first, the vigorous cambial growth, where- 
by incisions in the bark and wood rapidly heal up ; and, 
second, the extensive evaporation that goes on from 
foliage. 

That evaporation of water from the leaves often pro- 
ceeds more rapidly than it can be supplied by the roots 
is shown by the facts that the delicate leaves of many 
plants wilt when the soil about their roots becomes dry, 
that water is often rapidly sucked into wounds on the 
stems of trees which are covered with foliage, and that 
the proportion of water in the wood of the trees of tem- 
perate latitudes is least in the months of May, June, and 
July. 

Evergreens do not bleed in the spring-time. The oak 
loses little or no sap, and among other trees great diver- 
sity is noticed as to the amount of water that escapes at 
a wound on the stem. In case of evergreens we have a 
stem destitute of all proper vascular tissue, and admit- 



376 HOW CROPS GROW. 

ting a flow of liquid only through perforations of the 
wood-cells, if these really exist (which Sachs denies). 
Again, the leaves admit of continual evajDoration, and 
furnish an outlet to the water. The colored heart-wood 
existing in many trees is impervious to water, as shown 
by the experiments of Boucherie and Hartig.. Sap can 
only flow through the white, so-called sap-wood. In 
early June, the new shoots of the vine do not bleed when 
cut, nor does sap flow from the wounds made by break- 
ing them off close to the older stem, although a gash in 
the latter bleeds profusely. In the young branches, 
there are no channels that permit the rapid efflux of 
water. 

Composition of Sap. — The sap in all cases consists 
chiefly of water. This liquid, as it is absorbed, brings 
in from the soil a small proportion of certain saline mat- 
ters — the phosphates, sulphates, nitrates, etc., of potas- 
sium, calcium, and magnesium. It finds in the plant 
itself its organic ingredients. These may be derived 
from matters stored in reserve during a previous year, as 
in the spring sap of trees ; or may be newly formed, as 
in summer growth. 

The sugar of maple-sap, in spring, is undoubtedly pro- 
duced by the transformation of starch which is found 
abundantly in the wood in winter. According to Hartig 
(Jour, far Prakt. Gh., 5, p. 217, 1835), all deciduous 
trees contain starch in their wood and yield a sweet 
spring sap, while* evergreens contain little or no starch. 
Hartig reports having been able to procure from the root- 
wood of the horse-chestnut in one instance no less than 
26 per cent of starch. This is deposited in the tissues 
during summer and autumn, to be dissolved for the use 
of the plant in developing new foliage. In evergreens 
and annual plants the organic matters of the sap are 
derived more directly from the foliage itself. The leaves 
absorb carbon dioxide and unite its carbon to the ele- 



MOTION OF THE JUICES. 377 

ments of water, with the production of sugar and other 
carbhydrates. In the leaves, also, probably nitrogen 
from the nitrates and ammonia-salts gathered by the 
roots, is united to carbon, hydrogen, and oxygen, in the 
formation of albuminoids. 

Besides sugar, malic acid and minute quantities of 
proteids exist in maple sap. Towards the close of the 
sugar-season the sap appears to contain other organic 
substances which render the sugar impure, brown in 
color, and of different flavor. 

It is a matter of observation that maple-sugar is whiter, 
purer, and " grains " or crystallizes more readily in those 
years when spring-rains or thaws are least frequent. 
This fact would appear to indicate that the brown or- 
ganic matters which water extracts from leaf-mold may 
enter the roots of the trees, as is the belief of practical 
men. 

The spring-sap of many other deciduous trees of tem- 
perate climates contains sugar, but while it is cane sugar 
in the maple, in other trees it appears to consist mostly 
or entirely of dextrose. . 

Sugar is the chief organic ingredient in the juice of 
the sugar cane, Indian corn, beet, carrot, turnip, and 
parsnip. 

The sap that flows from the vine and from many cul- 
tivated herbaceous plants contains little or no sugar-; in 
that of the vine, gum or dextrin is found in its stead. 

What has already been stated makes evident that we 
cannot infer the quantity of sap in a plant from what 
may run out of an incision, for the sap that thus issues 
is for the most part water forced up from the soil. It is 
equally plain that the sap, thus collected, has not the 
normal composition of the juices of the plant; it must 
be diluted, and must be the more diluted the longer and 
the more rapidly it flows. 

Ulbricht has made partial analyses of the sap obtained 



378 HOW CROPS GROW. 

from the stumps of potato, tobacco, and sun-flower 
plants. He found that successive portions, collected 
separately, exhibited a decreasing concentration. In 
sunflower sap, gathered in five successive portions, the 
liter contained the following quantities (grams) of solid 
matter : 

1. 2. 3. 4. 5. 

Volatile substance,... 1.45 0.60 0.30 0.25 0.21 

Ash, 1.58 1.56 1.18 0.70 0.60 



Total, 3.03 2.16 1.48 0.95 0.81 

The water which streams from a wound dissolves and 
carries forward with it matters that, in the uninjured 
plant, would probably suffer a much less rapid and ex- 
tensive translocation. From the stump of a potato-stalk 
would issue, by the mere mechanical effect of the flow of 
water, substances generated in the leaves, whose proper 
movement in the uninjured plant would be downwards 
into the tubers. 

Different Kinds of Sap. — It is necessary at this 
point in our discussion to give prominence to the fact 
that there are different Jrinds of sap in the plant. As 
we have seen (p. 289), the cross section of the plant pre- 
sents two kinds of tissue, the cellular and vascular. 
These carry different juices, as is shown by their chemi- 
cal reactions. In the cell-tissues exist chiefly the non- 
nitrogenous principles, sugar, starch, oil, etc. The 
liquid in these cells, as Sachs has shown, commonly con- 
tains also organic acids and acid-salts, and hence gives a 
blue color to red litmus. In the vascular tissue albumin- 
oids preponderate, and the sap of the ducts commonly 
has an alkaline reaction towards test papers. These dif- 
ferent kinds of sap are not, however, always strictly con- 
fined to either tissue. In the root-tips and buds of 
many plants (maize, squash, onion), the young (new- 
formed) cell-tissue is alkaline from the preponderance of 



MOTION OF THE JUICES. 379 

albuminoids, while the spring sap flowing from the ducts 
and wood of the maple is faintly acid. 

In many plants is found a system of channels (milk- 
ducts, p. 30-i), independent of the vascular bundles, 
which contain an opaque, white, or yellow juice. This 
liquid is seen to exude from the broken stem of the milk- 
weed (Asclepias), of lettuce, or of celandine (Chelidon- 
ium), and may be noticed to gather in drops upon a 
fresh-cut slice of the sweet potato. The milky juice 
often differs, not more strikingly in appearance than it 
does in taste, from the transparent sap of the cell-tissue 
and vascular bundles. The former is commonly acrid 
and bitter, while the latter is sweet or simply insipid to 
the tongue. 

Motion of the Nutrient Matters of the Plant. — 
The occasional rapid passage of a current of water up- 
wards through the plant must not be confounded with 
the normal, necessary, and often contrary motion of the 
nutrient matters out of which new growth is organized, 
but is an independent or highly subordinate process by 
which the plant adapts itself to the constant changes 
that are taking place in the soil and atmosphere as re- 
gards their content of moisture. 

A plant supjidied with enough moisture to keep its tis- 
sues turgid is in a normal state, no matter whether the 
water within it is nearly free from upward flow or ascends 
rapidly to compensate the waste by evaporation. In 
both cases the motion of the matters dissolved in the sap 
is nearly the same. In both cases the plant develops 
nearly alike. In both cases the nutritive matters gath- 
ered at the root-tips ascend, and those gathered by the 
leaves descend, being distributed to every growing cell ; 
and these motions are comparatively independent of, and 
but little influenced by, the motion of the water in which 
they are dissolved. 

The upward flow of sap in the plant i« confined to the 



380 HOW CHOPS GROW. 

vascular bundles, whether these are arranged symmetri- 
cally and compactly, as in exogenous plants, or distrib- 
uted singly through the stem, as in the enclogens. This 
is not only seen upon a bleeding stump, but is made evi- 
dent by the oft-observed fact that colored liquids, when 
absorbed into a plant or cutting, visibly follow the course 
of the vessels, though they do not commonly penetrate 
the spiral ducts, but ascend in the sieve-cells of the cam- 
bium. * 

The rapid supply of water to the foliage of a plant, 
either from the roots or from a vessel in which the cut 
stem is immersed, goes on when the cellular tissues of 
the bark and pith are removed or interrupted, but is at 
once checked by severing the vascular bundles. 

The proper motion of the nutritive matters in the 
plant — of the salts disssolved from the soil and of the 
organic principles compounded from carbonic acid, water, 
and nitric acid or ammonia in the leaves — is one of slow 
diffusion, mostly through the walls of imperforate cells, 
and goes on in all directions. New growth is the forma- 
tion and expansion of new ceils into which nutritive 
substances are imbibed, but not poured through visible 
passages. When closed cells are converted into ducts or 
visibly communicate with each other by pores, their ex- 
pansion has ceased. Henceforth they merely become 
thickened by interior deposition. 

Movements of Nutrient Matters in the Bark or 
Rind. — The ancient observation of what ordinarily ensues 
when a ring of bark is removed from the stem of an exo- 
genous tree, led to the erroneous assumption of a form- 
al downward current of " elaborated " sap in the bark. 
When a cutting from one of our common trees is girdled 
at its middle and then placed in circumstances favorable 



* As in Unger's experiment of placing a hyacinth in the juice of the 

{)oke weed {Phytolacca), or in Hallier's observations on cuttings dipped 
n cherry-juice. ( Vs. St., IX, p. 1.) 



MOTION OF THE JUICES. 



381 




Fig.ee. 



for growth, as in moist, warm 
air, with its lower extremity 
in water, roots form chiefly 
at the edge of the bark jnst 
above the removed ring. The 
twisting, or half-breaking, as 
well as ringing of a layer, 
promotes the development of 
roots. Latent buds are often 
called forth on the stems of 
fruit trees, and branches grow 
more vigorously, by making 
a transverse incision through 
the bark just below the point 
of their issue. Girdling a 
fruit-bearing branch of the 
grape-vine near its junction 
with the older wood has the 
effect of greatly enlarging the 
fruit. It is well known that 
a wide wound made on the 
stem of a tree heals up by the 
formation of new wood, and 
commonly the growth is most 
rapid and abundant above the 
cut. From these facts it was 
concluded that sap descends 
in the bark, and, not being 
able to pass below a wound, 
leads to the organization of 
new roots or wood just above 
it. 

The accomprmying illustration, 
Fig. 66, represents the base of a cut- 
ting from an exogenous stem (pear 
or currant), girdled at B and kept 
for some days immersed in water to 
the depth indicated by the line L. 



382 now crops grow. 

The first maif estation of growth is the formation of a protuberance at 
the lower edge of the bark, which is known to gardeners as a callous, 
C. This is an extension of the cellular tissue. From the callous shortly 
appear rootlets, R, which originate from the vascular tissue. Rootlets 
also break from the stem above the callous and also above the water, 
if the air be moist. They appear, likewise, though in less number, 
below the girdled place. 

Nearly all the organic substances (carbhydrates, al- 
buminoids, acids, etc.) that are formed in a plant are 
produced in the leaves, and must necessarily find their 
way down to nourish the stem and roots. The facts 
just mentioned demonstrate, indeed, that they do go 
down in the bark. We have, however, no proof that 
there is a downward flow of sap. Such a flow is not 
indicated by a single fact, for, as we have before seen, 
the only current of water in the uninjured plant is the 
upward one which results from root-action and evapora- 
tion, and that is variable and mainly independent of the 
distribution of nutritive matters. Closer investigation 
has shown that the most abundant downward movement 
of the nutrient matters generated in the leaves proceeds 
in the thin-walled sieve-cells of the cambium, which, in 
exogens, is young tissue common to the outer wood and the 
inner bark — which, in fact, unites bark and wood. The 
tissues of the leaves communicate directly with, and are 
a continuation of, the cambium, and hence matters 
formed by the leaves must move most rapidly in the 
cambium. If they pass with greatest freedom through 
the sieve-cells, the fact is simply demonstration that the 
latter communicate most directly with those parts of the 
leaf in which the matters they conduct are organized. 

In endogenous plants and in some exogens (Piper me- 
dium, Amaranthus sanguineus), the vascular bundles 
containing sieve-cells pass into the pith and are not con- 
fined to the exterior of the stem. Girdling such plants 
does not give the result above described. With them, 
roots are formed chiefly or entirely at the base of the 
cutting (Hanstein), and not above the girdled place. 



MOTION OF THE Jl'iCES. 383 

In all cases, without exception, the matters organized 
in the leaves, though most readily and abundantly mov- 
ing downwards in the vascular tissues, are not confined 
to them exclusively. When a ring of bark is removed 
from a tree, the new cell-tissues, as well as the vascular, 
are interrupted. Notwithstanding, matters are trans- 
mitted downwards, through the older wood. When but 
a narrow ring of bark is removed from a cutting, roots 
often appear below the incision, though in less number, 
and the new growth at the edges of a wound on the 
trunk of a tree, though most copious above, is still de- 
cided below — goes on, in fact, all around the gash. 

Both the cell- tissue and the vascular thus admit of 
the transport of the nutritive matters downwards. In 
the former, the carbhydrates — starch, sugar, inulin — the 
fats, and acids, chiefly occur and move. In the large 
ducts, air is contained, except when by vigorous root- 
action the stem is surcharged with water. In the sieve- 
ducts (cambium) are found the albuminoids, though not 
unmixed with carbhydrates. If a tree have a deep gash 
cut into its stem (but not reaching to the colored heart- 
wood), growth is not suppressed on either side of the 
cut, but the nutritive matters of all kinds pass out of a 
vertical direction around the incision, to nourish the new 
wood above and below. Girdling a tree is not fatal, if 
done in the spring or early summer when growth is rapid, 
provided that the young cells, which form externally, 
are protected from dryness and other destructive influ- 
ences. An artificial bark, i. e., a covering of cloth or 
clay to keep the exposed wood moist and away from air, 
saves the tree until the wound heals over.* In these 
cases it is obvious that the substances which commonly 
preponderate in the sieve-ducts must pass through the 



* If the freshly exposed wood be rubbed or wiped with a eloth, 
whereby the moist cambial layer (of cells containing nuclei and capa- 
ble of multiplying) is removed, no growth can occur. Ratzeburg. 



384 HOW CROPS GROW. 

cell-tissue in order to reach the point where they nourish 
the growing organs. 

Evidence that nutrient matters also pass upwards in 
the bark is furnished, not only by tracing the course of 
colored liquids in the stem, but also by the fact that 
undeveloped buds perish in most cases when the stem is 
girdled between them and active leaves. In the excep- 
tions to this rule, the vascular bundles penetrate the 
pith, and thereby demonstrate that they are the chan- 
nels of this movement. A minority of these exceptions 
again makes evident that the sieve-cells are the path of 
transfer, for, as Hanstein has shown, in certain plants 
(SolanaceaB, Asclepiadeae, etc.), sieve-cells penetrate the 
pith unaccompanied by any other elements of the vascu- 
lar bundle, and girdled twigs of these plants grow above 
as well as beneath the wound, although all leaves above 
the girdled place be cut off, so that the nutriment of the 
buds must come from below the incision. 

The substances which are organized in the foliage of a 
plant, as well as those which are imbibed by the roots, 
move to any point where they can supply a want. Carb- 
hydrates pass from the leaves, not only downwards, to 
nourish new roots, but upwards, to feed the buds, flow- 
ers, and fruit. In case of cereals, the power of the 
leaves to gather and organize atmospheric food nearly or 
altogether ceases as they approach maturity. The seed 
grows at the expense of matters previously stored in the 
foliage and stems (p. 237), to such an extent that it may 
ripen quite perfectly although .the plant be cut when the 
kernel is in the milk, or even earlier, while the juice of 
the seeds is still watery and before starch-grains have 
begun to form. 

In biennial root-crops, the root is the focus of motion 
for the matters organized by growth during the first 
year ; but in the second year the stores of the root are 
completely exhausted for the support of flowers and seed, 



CAUSES OF THE MOTIOX OF JUICES. 385 

so that the direction of the movement of these organized 
matters is reversed. In both years the motion of water 
is always the same, viz., from the soil upwards to the 
leaves.* 

The summing up of the whole matter is that the nutri- 
ent substances in the plant are not absolutely confined 
to any path, and may move in any direction. The fact 
that they chiefly follow certain channels, and move m 
this or that direction, is plainly dependent upon the 
structure and arrangement of the tissues, on the sources 
of nutriment, and on the seat of growth or other action. 



§3. 



THE CAUSES OF MOTION OF THE VEGETABLE JUICES. 

Porosity of Vegetable Tissues. — Porosity is a 
property of all the vegetable tissues and implies that the 
molecules or smallest particles of matter composing the tis- 
sues are separated from each other by a certain space. In 
a multitude of cases bodies are visibly porous. In many 
more we can see no pores, even by the aid of the highest 
magnifying powers of the microscope ; nevertheless the 
fact of porosity is a necessary inference from another 
fact which may be observed, viz., that of absorption. A 
fiber of linen, to the unassisted eye, has no pores. 
Under the microscope we 6nd that it is a tubular cell, 
the bore being much less than the thickness of the walls. 
By immersing it in water it swells, becomes more trans- 
parent, and increases in weight. If the water be colored 
by solution of indigo or cochineal, the fiber is visibly 

* The motion of water is always upwards, because the soil always 
contains more water than the air. If a plant were so situated that its 
roots should steadily lack water while its foliage had an excess of this 
liquid, it cannot be doubted that then the "sap" would pass down in 
a regular flow. In this case, nevertheless, the nutrient matters would 
take their normal course. 

25 



386 HOW CROPS GROW. 

penetrated by the dye. It is therefore porous, not only 
in the sense of having an interior cavity which becomes 
visible by a high magnifying power, but likewise in hav- 
ing throughout its apparently imperforate substance in- 
numerable channels in which liquids can freely pass. 
In like manner, all the vegetable tissues are more or less 
penetrable to water. 

Imbibition of Liquids by Porous Bodies. — Not 
oniv do the tissues of the plant admit of the access of 
water into their pores, but they forcibly drink in or 
aosoro tms liquid, when it is presented to them in excess, 
until their pores are full. 

When the molecules of a porous body have freedom 
of motion, they separate from each other on imbibing a 
liquid ; the body itself swells. Even powdered glass or 
line sand perceptibly increases in bulk by imbibing water. 
Clay swells much more. Gelatinous silica, pectin, gum 
tragacanth, and boiled starch hold a vastly greater amount 
of water in their pores or among their molecules. 

In case of vegetable and animal tissues, or membranes, 
we find a greater ov less degrecof expansibility from the 
same cause, but here the structural connection of the 
molecules puts a limit to their separation, and the result 
of saturating them with a liquid is a state of turgidity 
and tension, which subsides to one of yielding flabbiness 
when the liquid is partially removed. 

The energy with which vegetable matters imbibe water 
may be gathered from a well-known fact. In granite 
quarries, long blocks of stone are split out by driving 
plugs of dry wood into holes drilled along the desired 
line of fracture and pouring water over the plugs. The 
liquid penetrates the wood with immense force, and the 
toughest rock is easily broken apart. 

The imbibing power of different tissues and vegetable 
matters is widely diverse. In general, the younger or- 
gans or parts take up water most readily and freely. The 



CAUSES OF THE MOTION OF JUICES. 38? 

sap-wood of trees is far more absorbent than the heart- 
wood and bark. The cuticle of the leaf is often com- 
paratively impervious to water. Of the proximate ele- 
ments we have cellulose and starch-grains able to retain, 
even when air-dry, 10 to 15% of water. Wax and the 
solid fats, as well as resins, on the contrary, do not 
greatly attract water, and cannot easily be wetted with 
it. They render cellulose, which has been impregnated 
with them, unabsorbent. 

Those vegetable substances which ordinarily manifest 
the greatest absorbent power for water, are the gummy 
carbhydrates and the albuminoids. In the living plant 
the protoplasmic membrane exhibits great absorbent 
power. Of mineral matters, gelatinous silica (Exp. 58, 
p. 137) is remarkable on account of its attraction for 
water. 

Not only dg diiferent substances thus exhibit unlike 
adhesion to water, but the same substance deports itself 
variously towards different liquids. 

One hundred parts of dry ox-bladder were found by 
Liebig to absorb during 24 hours : — 

268 parts of pure Water. 

133 " " saturated Brine. 

38 " » Alcohol (84%). 

17 " " Bone-oil. 

A piece of dry leather will absorb either oil or water, 
and apparently with equal avidity. If, however, oiled 
leather be immersed in water, the oil is gradually and 
perfectly displaced, as the farmer well knows from, his 
experience with greased boots. India-rubber, on the 
other hand, is impenetrable to water, while oil of tur- 
pentine is imbibed by it in large quantity, causing the 
caoutchouc to swell up to a pasty mass many times its 
original bulk. 

The absorbent power is influenced by the size of the 
pores. Other things being equal, the finer these are, the 
greater the force with which a liquid is imbibed. This 



388 HOW CROPS GROW. 

is shown by what has been learned from the study of a 
kind of pores whose effect admits of accurate measure- 
ment. A tube of glass, with a narrow, uniform caliber, 
is such a pore. In a tube of 1 millimeter (about ^ of 
an inch), in diameter, water rises 30 mm. In a tube of 
-^o millimeter, the liquid ascends 300 mm. (about 11 
inches) ; and, in a tube of r fo mm., a column of 3,000 
mm. is sustained. In porous bodies, like chalk, plaster 
stucco, closely packed ashes or starch, Jamin found that 
water was absorbed with force enough to overcome the 
pressure of the atmosphere from three to six times ; in 
other words, to sustain a column of water in a wide 
tube 100 to 200 ft. high. (Comptes Benches, 50, p. 311.) 

Absorbent power is influenced by temperature. Warm 
water is absorbed by wood more quickly and abundantly 
than cold. In cold water starch does not swell to any 
striking or even perceptible degree, although consider- 
able liquid is imbibed. In hot water, however, the case 
is remarkably altered. The starch-grains are forcibly 
burst open, and a paste or jelly is formed that holds 
many times its weight of water. (Exp. 27, p. 51.) On 
freezing, the particles of water are mostly withdrawn 
from their adhesion to the starch. The ascent of liquids 
in narrow tubes whose walls are unabsorbent, is, on the 
contrary, diminished by a rise of temperature. 

Adhesive Attraction.— The absorption of a liquid 
into the cavities of a porous body, as well as its rise in a 
narrow tube, are expressions of the general fact that 
there is an attraction between the molecules of the liquid 
and the solid. In its simplest manifestation this attrac- 
tion exhibits itself as Adhesion, and this term we shall 
employ to designate the kind of force under considera- 
tion. If a clean plate of glass be dipped in water, the 
liquid touches, and sticks to, the glass. On withdraw- 
ing the glass, a film of water comes away with it — the 
adhesive force of water to glass being greater than the 
cohesive force among the water molecules. 



CAUSES OF THE MOTION OF JUICES. 389 

Capillary Attraction. — If two squares of glass be 
set up together upon a plate, so that they shall be 
in contact at their vertical edges on one side, and one- 
eighth of an inch apart on the other, it will be seen, on 
pouring a little water upon the plate, that this liquid 
rises in the space between them to a hight of several 
inches where they are in very near proximity, and curves 
downwards to their base where the interval is large. 

Capillary attraction, which thus causes liquids to rise 
in narrow channels or fine tubes, involves indeed the 
adhesion of the liquid to the walls of the tube, but also 
depends on a tension of the surface of the liquid, due to 
the fact that the molecules at the surface only attract 
and are only attracted by underlying molecules, so that 
they exert a pressure on the mass of liquid beneath them. 
Where the liquid adheres to the sides of a containing 
tube or cavity, this pressure is diminished and there the 
liquid rises. 

Adhesion may be a Cause of Continual Move- 
ment under certain circumstances. When a new cotton 
wick is dipped into oil, the motion of the oil may be fol- 
lowed by the eye, as it slowly ascends, until the pores 
are filled and motion ceases. Any cause which removes 
oil from the pores at the apex of the wick will disturb 
the equilibrium which had been established between the 
solid and the liquid. A burning match held to the 
wick, by its heat destroys the oil, molecule after mole- 
cule, and this process becomes permanent when the wick 
is lighted. As the pores at the base of the flame give up 
oil to the latter, they fill themselves again from the 
pores beneath, and the motion thus set up propagates 
itself to the oil in the vessel below and continues as long 
as the flame burns or the oil holds out. 

We get a further insight into the nature of this motion 
when we consider what happens after the oil has all been 
sucked up into the wick. Shortly thereafter the dimen- 



390 HOW CROPS GROW. 

sions of the flame are seen to diminish. It does not, 
however, go out, but burns on for a time with continually 
decreasing vigor. When the supply of liquid in the por- 
ous body is insufficient to saturate the latter, there is 
still the same tendency to equalization and equilibrium. 
If, at last, when the flame expires, because the combus- 
tion of the oil falls below that rate which is needful to 
generate heat sufficient to decompose it, the wick be 
placed in contact at a single point, with another dry 
wick of equal mass and porosity, the oil remaining in 
the first will enter again into motion, will pass into the 
second wick, from pore to pore, until the oil has been 
shared nearly equally between them. 

In case of water contained in the cavities of a porous 
body, evaporation from the surface of the latter becomes 
remotely the cause of a continual upward motion of the 
liquid. 

The exhalation of water as vapor from the foliage of a 
plant thus necessitates the entrance of water as liquid 
at the roots, and maintains a flow of it in the sap-ducts, 
or causes it to pass by absorption from cell to cell. 

Liquid Diffusion. — The movements that proceed in 
plants, when exhalation is out of the question, viz., such 
as are manifested in the stump of a vine cemented into a 
gauge (Fig. 43, p. 248), are not to be accounted for by 
capillarity or mere absorptive force under the conditions 
as yet noticed. To approach their elucidation we require 
to attend to other considerations. 

The particles of many different kinds of liquids attract 
each other. Water and alcohol may be mixed together 
in all proportions in virtue of their adhe ive attraction. 
If we fill a vial with water to the rim and carefully lower 
it to the bottom of a tall jar of alcohol, we shall find 
after some hours that alcohol has penetrated the vial, 
and water has passed out into the jar, notwithstanding 
the latter liquid is considerably heavier than the former. 



CAUSES OF THE MOTION OF JUICES. 391 

If the water be colored by indigo or cherry juice, its 
motion may be followed by the eye, and after a certain 
lapse of time the water and alcohol will be seen to have 
become uniformly mixed throughout the two vessels. 
This manifestation of adhesive attraction is termed Liq- 
uid Diffusion, 

What is true of two liquids likewise holds for two 
solutions, i. e., for two solids made liquid by the action 
of a solvent. A vial filled with colored brine, or syrup, 
and placed in a vessel of water, will discharge its con- 
tents into the latter, itself receiving water in return ; 
and this motion of the liquids will not cease until the 
whole is uniform in composition, i. e., until every mole- 
cule of salt or sugar is equally attracted by all the mole- 
cules of water. 

When several or a large number of soluble substances 
are placed together in water, the diffusion of each one 
throughout the entire liquid will go on in the same way 
until the mixture is homogeneous. 

Liquid Diffusion may be a Cause of Continual 
Movement whenever circumstances produce continual 
disturbances in the composition of a solution or in that 
of a mixture of liquids. 

If into a mixture of two liquids we introduce a solid 
body which is able to combine chemically with, and 
solidify one of the liquids, the molecules of this liquid 
will begin to move toward the solid body from all points, 
and this motion will cease only when the solid is able to 
combine with no more of the one liquid, or no more 
remains for it to unite with. Thus, when quicklime is 
placed in a mixture of alcohol and water, the water is in 
time completely condensed in the lime, and the alcohol 
is rendered anhydrous. 

Rate of Diffusion. — The rate of diffusion varies with 
the nature of the liquids ; if solutions, with their degree 
of concentration and with the temperature. 



393 HOW CROPS GROW. 

Colloids arid Crystalloids. — There is a class of bodies 
whose molecules are singularly inactive in many respects, 
and have, when dissolved in water or other liquid, a 
very low capacity for diffusive motion. These bodies 
are termed Colloids,* and are characterized by swelling 
up or uniting with water to bulky masses (hydrates) of 
gelatinous consistence, by inability to crystallize, and by 
feeble and poorly-defined chemical affinities. Starch, 
dextrin, the gums, the albuminoids, pectin and pectic 
acid, gelatin (glue), tannin, the hydroxides of iron and 
aluminium and gelatinous silica, are colloids. Opposed 
to these, in the properties just specified, are those bodies 
which crystallize, such as saccharose, glucose, oxalic, 
citric, and tartaric acids, and the ordinary salts. 

Other bodies which have never been seen to crystallize 
have the same high diffusive rate ; hence the class is 
termed by Graham Crystalloids. \ 

Colloidal bodies, when insoluble, are capable of imbib- 
ing liquids, and admit of liquid diffusion through their 
molecular interspaces. Insoluble crystalloids are, on 
the other hand, impenetrable to liquids in this sense. 
The colloids swell up more or less, often to a great bulk, 
from absorbing a liquid ; the volume of a crystalloid 
admits of no such change. 

In his study of the rates of diffusion of various sub- 
stances, dissolved in water to the extent of one per cent 
of the liquid, Graham found the following 

APPROXIMATE TIMES OF EQUAL DIFFUSION. 

Hydrochloric acid, Crystalloid, 1. 

Sodium Chloride, " 2J. 

Cane Sugar, " 7. 

Magnesium Sulphate, " 7. 

Albumin, Colloid, 49. 

Caramel, " 98. 



* From two Greek words which signify glue-like. 

t We have already employed the word Crystalloid to distinguish the 
amorphous albuminoids from their modifications or combinations 
which present the aspect of crystals (p. 107). This use of the word was 
proposed by Xageli, in 1862. Graham had employed it, as opposed to 
colloid, in 1861. 



CAUSES OF THE MOTION OF JUICES. 393 

The table shows that the diffusive activity of hydro- 
chloric acid through water is 98 times as great as that of 
caramel (see p. G6, Exp. 29). In other words, a mole- 
cule of the acid will travel 98 times as far in a given 
time as the molecule of caramel. 

Osmose,* or Membrane Diffusion. — When two 
miscible liquids or solutions are separated by a porous 
diaphragm, the phenomena of diffusion (which depend 
upon the mutual attraction of the molecules of the dif- 
ferent liquids or dissolved substances) are complicated 
with those of imbibition or capillarity, and of chemical 
affinity. The adhesive or other force which the septum 
is able to exert upon the liquid molecules supervenes 
upon the mere diffusive tendency, and the movements 
may suffer remarkable modifications. 

If we should separate pure water and a solution of 
common salt by a membrane upon whose substance these 
liquids could exert no action, the diffusion would pro- 
ceed to the same result as were' the membrane absent. 
Molecules of water would penetrate the membrane on 
one side and molecules of salt on the other, until the 
liquid should become alike on both. Should the water 
move faster than the salt, the volume of the brine would 
increase, and that of the water would correspondingly 
diminish. Were the membrane fixed in its place, a 
change of level of the liquids would occur. Graham has 
observed that common salt actually diffuses into water, 
through a thin membrane of ox-bladder deprived of its 
outer muscular coating, at very nearly the same rate as 
when no membrane is interposed. 

Dutrochet was the first to study the phenomena of 
membrane diffusion. He took a glass funnel with a long 
and slender neck, tied a piece of bladder over the wide 
opening, inverted it, poured in brine until the funnel 
was filled to the neck, and immersed the bladder in a 

* From a Greek word meaning impulsion. 



394 



HOW CROPS GROW 



vessel of water. He saw the liquid rise in the narrow 
tube and fall in the outer vessel. He designated the 
passage of water into the funnel as endosmose, or inward 
propulsion. At the same time he found the water sur- 
rounding the fnnnel to acquire the taste of salt. The 
outward transfer of salt was his exosmose. The more 
general word, Osmose, expresses both phenomena ; we 
may, however, employ Dutrochet's 
terms to designate the direction of 
osmose. 

Osmometer. — "When the apparatus 
employed by Dutrochet is so con- 
structed that the diameter of the nar- 
row tube has a known relation to, is, 
for example, exactly one -tenth that of 
the membrane, and the narrow tube 
itself is provided with a millimeter 
scale, we have the Osmometer of Grah- 
am, Fig 67. The ascent or descent of 
the liquid in the tube gives a measure 
of the amount of osmose, provided the 
hydrostatic pressure is counterpoised 
by making the level of the liquid with- 
in and without equal, for which pur- 
pose water is poured into or removed from the outer ves- 
sel. Graham designates the increase of volume in the 
osmometer as positive osmose, or simply osmose, and dis- 
tinguishes the fall of liquid in the narrow tube as nega- 
tive osmose. 

In the figure, the external vessel is intended for the reception of 
water. The funnel-shaped interior vessel is closed below with mem- 
brane, and stands upon a shelf of perforated zinc for support. The 
graduated tube fits the neck of the funnel by a ground joint. 

Action of the Membrane. — When an attraction exists 
the membrane itself and one or more of the substances 
between which it is interposed, then the rate, amount, 
and even direction, of diffusion may be greatly changed. 




Fis. 67. 



CAUSES OF THE MOTION OF JUICES. 395 

Water is imbibed by the membrane of bladder much 
more freely than alcohol ; on the other hand, a film of 
collodion (cellulose nitrate left from the evaporation of 
its solution in ether) is penetrated much more easily by 
alcohol than by water. If, now, these liquids be sepa- 
rated by bladder, the apparent flow will be towards the 
alcohol ; but if a membrane of collodion divide them, 
the more rapid motion will be into the water. 

When a vigorous chemical action is exerted upon the 
membrane by the liquid or the dissolved matters, osmose 
is greatly heightened. In experiments with a septum of 
porous earthenware (porcelain biscuit), Graham found 
that in case of neutral organic bodies, as sugar and alco- 
hol, or neutral salts, like the alkali-chlorides and nitrates, 
very little osmose is exhibited, i. e. ? the diffusion is not 
perceptibly greater than it would be in absence of the 
porous diaphragm. 

The acids, — oxalic, nitric, and hydrochloric, — mani- 
fest a sensible but still moderate osmose. Sulphuric 
and phosphoric acids, and salts having a decided alka- 
line or acid reaction, viz., acid potassium oxalate, sodi- 
um phosphate, and carbonates of potassium and sodium, 
exhibit a still more vigorous osmose. For example, a 
solution of one part of potassium carbonate in 1,000 
parts of water gains volume rapidly, and to one part of 
the salt that passes into the water 500 parts of water 
enter the solution. 

In all cases where diffusion is greatly modified by a 
membrane, the membrane itself is strongly attacked and 
altered, or dissolved, by the liquids. When animal 
membrane is used, it constantly undergoes decomposi- 
tion and its osmotic action is exhaustible. In case 
earthenware is employed as a diaphragm, portions of its 
calcium and aluminium are always attacked and dis- 
solved by the solutions upon which it exerts osmose. 

Graham asserts that to induce osmose in bladder, the 



396 HOW CROPS GROW. 

chemical action on the membrane must be different on 
the two sides, and apparently not in degree only, but 
also in kind, viz., an alkaline action on the albuminoid 
substance of the membrane on the one side, and an acid 
action on the other. The water appears always to accu- 
mulate on the alkaline or basic side of the membrane. 
Hence, with an alkaline salt, like potassium carbonate, 
in the osmometer, and water outside, the flow is inwards ; 
but with an acid in the osmometer, there is negative 
osmose, or the flow is outwards, the liquid then falling 
in the tube. 

Osmotic activity is most highly manifested in such 
salts as easily admit of decomposition with the setting 
free of a part of their acid, or alkali. 

Hydration of the membrane. — It is remarkable 
that the rapid osmose of potassium carbonate and other 
alkali-salts is greatly interfered with by common salt, is, 
in fact, reduced to almost nothing by an equal quantity 
of this substance. In this case it is probable that the 
physical effect of the salt, in diminishing the power of 
the membrane to imbibe water (p. 393), operates in a 
sense inverse to, and neutralizes the chemical action of, 
the carbonate. In fact, the osmose of the carbonate, as 
well as of all other salts, acid or alkaline, may be due to 
their effect in modifying the hydration* or power of the 
membrane, to imbibe the liquid, which is the vehicle of 
their motion. Graham suggests this view as an explana- 
tion of the osmotic influence of colloid membranes, and 
it is not unlikely that in case of earthenware, the chem- 
ical action may exert its effect indirectly, viz., by pro- 
ducing bydrated silicates from the burned clay, which 
are truly colloid and analogous to animal membranes in 
respect of imbibition. Graham has shown a connection 
between the hydrating effect of acids and alkalies on 
colloid membranes and their osmotic rate. 



* In case wetter is employed as the liquid. 



CAUSES OF THE MOTION OF JUICES. 397 

"It is well known that fibrin, albumin, and animal 
membrane swell much more in very dilute acids and 
alkalies than in pure water. On the other hand, when 
the proportion of acid or alkali is carried beyond a point 
peculiar to each substance, contraction of the colloid 
takes place. The colloids just named acquire the power 
of combining with an increased proportion of water 
and of forming higher gelatinous hydrates in conse- 
quence of contact with dilute acid or alkaline reagents. 
Even parchment-paper is more elongated in an alkaline 
solution than in pure water. When thus hydrated 
and dilated, the colloids present an extreme osmotic 
sensibility." 

An illustration of membrane-diffusion which is highly 
instructive and easy to produce, is the following : 

A cavity is scooped out in a carrot, as in Fig. 68, so 
that the sides remain £ inch or so thick, 
and a quantity of dry, crushed sugar is 
introduced ; after some time, the previ- 
ously dry sugar will be converted into a 
syrup by withdrawing water from the flesh 
of the carrot. At the same time the latter 
] / will visibly shrink from the loss of a por- 

' tion of its liquid contents. In this case 

Fig. 68. ^Yie small portions of juice moistening the 
cavity form a strong solution with the sugar in contact 
w r ith them, into which water diffuses from the adjoining 
cells. Doubtless, also, sugar penetrates the parenchyma 
of the carrot. 

In the same manner, sugar, when sprinkled over thin- 
skinned fruits, shortly forms a syrup with the water 
which it thus withdraws from them, and salt packed 
with fresh meat runs to brine by the exosmose of the 
juices of the flesh. In these cases the fruit and the 
meat shrink as a result of the loss of water. 

Graham observed gum tra^acanth, which is insoluble 




398 HOW CROPS GEOW. 

in water, to cause a rapid passage of water through a 
membrane in the same manner from its power of imbibi- 
tion, although here there could be no exosmose or out- 
ward movement. 

The application of these facts and principles to explain- 
ing the movements of the liquids of the plant is obvious. 
The cells and the tissues composed of cells furnish pre- 
cisely the conditions for the manifestation of motion by 
the imbibition of liquids and by simple diffusion, as well 
as by osmose. The disturbances needful to maintain 
motion are to be found in the chemical changes that 
accompany the processes of nutrition. The substances 
that normally exist in the vegetable cells are numerous, 
and they suffer remarkable transformations, both in 
chemical constitution and in physical properties. The 
rapidly-diffusible salts that are presented to the plant by 
the soil, and the equally diffusible sugar and organic 
acids that are generated in the leaf-cells, are, in part, 
converted into the sluggish, soluble colloids, soluble 
starch, dextrin, albumin, etc., or are deposited as solid 
matters in the cells or upon their walls. Thus the dif- 
fusible contents of the plant not only, but the mem- 
branes which occasion and direct osmose, are subject to 
perpetual alterations in their nature. More than this, 
the plant grows ; new cells, new membranes, new pro- 
portions of soluble and diffusible matters, are unceas- 
ingly brought into existence. Imbibition in the cell- 
membranes and their solid, colloid contents, Diffusion 
in the liquid contents of the individual cells, and Osmose 
between the liquids and dissolved matters and the mem- 
branes, or colloid contents of the cells, must unavoid- 
ably take place. 

That we cannot follow the details of these kinds of 
action in the plant does not invalidate the fact of their 
operation. The plant is so complicated and presents 
such a number and variety of changes in its growth, 



CAUSES OF THE MOTION OF JUICES. 399 

that we can never expect to understand all its mysteries. 
From what has been briefly explained, we can compre- 
hend some of the more striking or obvious movements 
that proceed in the vegetable organism. 

Absorption and Osmose in Germination. — The 
absorption of water by the seed is the first stej) in Ger- 
mination. The coats of the dry seed, when put into the 
moist soil, imbibe this liquid which follows the cell-walls, 
from cell to cell, until these membranes are saturated 
and swollen. At the same time these membranes occa- 
sion or permit osmose into the cell-cavities, which, dry 
before, become distended with liquid. The soluble con- 
tents of the cells, or the soluble results of the transforma- 
tion of their organized matters, diffuse from cell to cell 
in their passage to the expanding embryo. 

The quantity of water imbibed by the air-dry seed commonly 
amounts to 50 and may exceed 100 per cent. R. Hoffmann has made 
observations on this subject (Vs. St. y VU, p. 50). The absorption was 
usually complete in 48 or 72 hours, and was as follows- in case of certain 
agricultural plants:— 

Per cent. Per cent. 

Mustard . . a 8.0 I Oats 59.8 

Millet 25.0 J Hemp 60.0 

Maize 44.0 i Kidney Bean 96.1 

Wheat 45.5 Horse Bean 104.0 



Buckwheat 46.8 

Barley 48.2 

Turnip 51.0 

Rye 57.7 



Pea 106.8 

Clover 117.5 

Beet 120.5 

White Clover 126.7 



Root-Action. — Absorption at the roots is unquestion- 
ably an osmotic action exercised by the membrane that 
bounds the young rootlets and root-hairs externally. In 
principle it does not differ from the absorption of water 
by the seed. The mode in which it occasions the sur- 
prising phenomena of bleeding or rapid flow of sap from 
a wound on the trunk or larger roots is doubtless essen- 
tially as Hofmeister first elucidated by experiment. 

This flow proceeds in the ducts and wood-ceils. 
Between these and the soil intervenes loose cell-tissue 



400 



HOW CROPS GROW. 



A 



surrounded by a compacter epidermis. Osmose takes 
place in the epidermis with such energy as not only to 
distend to its utmost the cell-tissue, but to cause the 
water of the cells to filter through their walls, and thus 
gain access to the ducts. The latter are formed in young 
cambial tissue, and, when new, are very delicate in their 
walls. 

Fig. 69 represents a simple apparatus by Sachs for 
imitating the supposed mechanism and process of Root- 
action. In the Fig., g g represents a short, wide, open 
glass tube ; at a, the tube is tied over and se- 
curely closed by a piece of pig's bladder ; it is then 
filled with solution of sugar, and the other end, 
b, is closed in similar manner by a piece of parch- 
ment-paper (p. 59). Finally a cap of India-rub- 
ber, K, into whose neck a narrow, bent glass 
tube, r, is fixed, is tied on over b. (These join- 
ings must be made very carefully and firmly.) 
The space within r iTis left empty of liquid, and 
the combination is placed in a vessel of water, as 
in the figure. C represents a root-cell whose 

exterior Avail (cuticle), 
a, is less penetrable 
under pressure than its 
interior, b; r corres- 
ponds to a duct of vas- 
cular tissue, and the 
surrounding water 
takes the place of that 
Fig. 09. existing in the pores of 

the soil. The water shortly penetrates the cell, C, dis- 
tends the previously flabby membranes, under the accu- 
mulating tension filters through b into r, and rises in 
the tube ; where in Sachs's experiment it attained a 
height of 4 or 5 inches in 24 to 48 hours, the tube, r, 
being about 5 millimeters wide and the area of b, 700 sq. 



r 




CAUSES OP THE MOTIOX OF JUICES. 401 

mm. When we consider the vast root-surface exposed 
to the soil, in case of a vine, and that myriads of root- 
lets and root-hairs unite their action in the compara- 
tively narrow stem, we must admit that the apparatus 
above figured gives us a very satisfactory glance into the 
causes of bleed in sr. 

Motion of Nutritive or Dissolved Matters; Se- 
lective Power of the Plant.— The motion of the sub- 
stances that enter the plant from the soil in a state of 
solution, and of those organized within the plant is, to a 
great degree, separate from and independent of that 
which the water itself takes. At the same time that 
water is passing upwards through the plant to make 
good the waste by evaporation from the foliage, sugar or 
other carbhvdrate generated in the leaves is diffusing 
against the water, and rinding its way down to the very 
root-tips. This diffusion takes place mostly in the cell- 
tissue, and is undoubtedly greatly aided by osmose, i. e., 
by the action of the membranes themselves. The very 
thickening of the cell-walls by the deposition of cellulose 
would indicate an attraction for the material from which 
cellulose is organized. The same transfer goes on sim- 
ultaneously in all directions, not only into roots and 
stem, but into the new buds, into flowers and fruit. 
We have considered the tendency to equalization between 
two masses of liquid separated from each other by pen- 
etrable membranes. This tendency makes valid for the 
organism of the plant the law that demand creates sup- 
ply. In two contiguous cells, one of -which contains 
solution of sugar, and the other solution of potassium 
nitrate, these substances must diffuse until they are 
mingled equally, unless, indeed, the membranes or some 
other substance present exerts an opposing and prepon- 
derating attraction. 

In the simplest phases of diffusion each substance is, 
to a certain degree, independent of every other. Any 
26 



402 HOW CROPS GROW. . 

salt dissolved in the water of the soil must diffuse into 
the root-cells of a plant, if it be absent from the sap of 
this root-cell and the membrane permit its passage. 
When the root-cell has acquired a certain proportion of 
the salt, a proportion equal to that in the soil-water, 
more cannot enter it. So soon as a molecule of the salt 
has gone on into another cell or been removed from the 
sap by any chemical transformation, then a molecule 
may and must enter from without. 

Silica is much more abundant in grasses and cereals 
than in leguminous plants. In the former it exists to 
the extent of about 25 parts in 1,000 of the air-dry foli- 
age, while the leaves and stems of the latter contain but 
3 parts. When these crops grow side by side, their 
roots are equally bathed by the same soil-water. Silica 
enters both alike, and, so far as regards itself, brings 
the cell-contents to the same state of saturation that 
exists in the soil. The cereals are able to dispose of 
silica by giving it a place in the cuticular cells ; the 
leguminous crops, on the other hand, cannot remove it 
from their juices ; the latter remain saturated, and thus 
further diffusion of silica from without becomes impos- 
sible except as room is made by new growth. It is in 
this way that we have a rational and adequate explana- 
tion of the selective power of the plant, as manifested 
in its deportment towards the medium that invests its 
roots. The same principles govern the transfer of mat- 
ters from cell to cell, or from organ to organ, within the 
plant. Wherever there is unlike composition of two 
miscible juices, diffusion is thereby set up, and proceeds 
as long as the cause of disturbance lasts, provided im- 
penetrable membranes do not intervene. The rapid 
movement of water goes on because there is great loss of 
this liquid ; the slow motion of silica is a consequence 
of the little use that arises for it in the plant. 

Strong chemical affinities may be overcome by help of 



CAUSES OF THE MOTION OF JUICES. 403 

osmose. Graham long ago observed the decomposition 
of alum (sulphate of aluminium and potassium) by mere 
diffusion ; its potassium sulphate having a higher diffu- 
sive rate than its aluminium sulphate. In the same 
manner acid potassium sulphate, put in contact with 
water, separates into neutral potassium sulphate and 
tree sulphuric acid.* 

AVe have seen (pp. 170-1) that the plant, when veg- 
etating in solutions of salts, is able to decompose them. 
It separates the components of potassium nitrate — appro- 
priating the acid and leaving the base to accumulate in 
the liquid. It resolves chloride of ammonium, — taking 
up ammonia and rejecting the hydrochloric acid. The 
action in these cases we cannot definitely explain, but 
our analogies leave no doubt as to the general nature of 
the agencies that cooperate to such results. 

The albuminoids in their usual form are colloid 
bodies, and very slow of diffusion through liquids. 
They pass a collodion membrane somewhat (Schu- 
macher), but can scarcely penetrate parchment-paper 
(Graham). In the plant they are found chiefly in the 
sieve-cells and adjoining parts of the cambium. Since 
for their production they must ordinarily require the 
concourse of a carbhydrate and a nitrate, they are not 
unlikely generated in the cambium itself, for here the 
descending carbhydrates from the foliage come in con- 
tact with the nitrates as they rise from the soil. On the 
other hand, the albuminoids become more diffusible in 
some of their combinations. Schumacher asserts that 
carbonates and phosphates of the alkalies considerably 
increase the osmose of albumin through collodion mem- 
branes (Phj/sih der Pflanzen, p. 128). It is probable that 
those combinations or modifications of the albuminoids 



*The decomposition of these salts is begun by the water in which 
they are dissolved, and is carried on by osmose, because the latter 
secures separation of the reacting substances. 



404 HOW CROPS GROW. 

whicli occur in the soluble crystalloids of aleurone 
(p. 105) and haemoglobin (p. 97) are highly diffusible, 
as certainly is the case with the peptones. 

Gaseous bodies, especially the carbonic acid and oxy- 
gen of the atmosphere, which have free access to the 
intercellular cavities of the foliage, and which are for the 
most part the only contents of the larger ducts, may be 
distributed throughout the plant by osmose after having 
been dissolved in the sap or otherwise absorbed by the 
cell-contents. 

Influence of the Membranes. — The sharp separa- 
tion of unlike juices and soluble matters in the plant 
indicates the existence of a remarkable variety and range 
of adhesive attractions. In orange-colored flowers we 
see upon microscopic examination that this tint is pro- 
duced by the united effect of yellow and red pigments 
whicli are contained in the cells of the petals. One cell 
is filled with yellow pigment, and the adjoining one with 
red, but these two colors are never contained in the 
same cell. In fruits we have coloring matters of great 
tinctorial power and freely soluble in water, but they 
never forsake the cells where they appear, never wander 
into the contiguous parts of the plant. In the stems 
and leaves of the dandelion, lettuce, and many other 
plants, a white, milky, and bitter juice is contained, but 
it is strictly confined to certain special channels and 
never visibly passes beyond them. The loosely disposed 
cells of the interior of leaves contain grains of chloro- 
phyl, but this substance does not appear in the epidermal 
cells, those of the stomata excepted. Sachs found that 
solution of indigo quickly entered the roots of a seedling 
bean, but required a considerable time to penetrate the 
stem. Hallier, in his experiments on the absorption of 
colored liquids by plants, noticed, in all cases when 
leaves or green stems were immersed in solution of indigo, 
or black-cherry juice, that these d\ r es readily passed into 



CAUSES OF THE MOTION OF JUICES. 405 

and colored the epidermis, the vascular and cambial tis- 
sue, and the parenchyma of the leaf-veins, keeping 
strictly to the cell-walls, but in no instance communi- 
cated any color to the cells containing chlorophyl. 
(Phytopathologie, Leipzig, 1868, p. 67.) We must infer 
that the coloring matters either cannot penetrate the 
cells that are occupied with chlorophyl, or else are chem- 
ically transformed into colorless substances on entering 
them. 

Sachs has shown in numerous instances that the juices 
of the sieve-cells and cambial tissue are alkaline, while 
those of the adjoining cell-tissue are acid when examined 
by test-paper. (Exp. Phys. tier Pflanzen, p. 394.) 

When young and active cells are moistened with solu- 
tion of iodine, this substance penetrates the cellulose 
without producing visible change, but when it "acts upon 
the protoplasm, the latter separates from the outer cell- 
wall and collapses towards the center of the cavity, as if 
its contents passed out, without a corresponding endos- 
mose being possible (p. 224). 

We may conclude from these facts that the membranes 
of the cells are capable of effecting and maintaining the 
separation of substances which have considerable attrac- 
tions for each other, and obviously accomplish this result 
by exerting their superior attractive or repulsive force. 

The influence of the membrane must vary in character 
with those alterations in its chemical and structural con- 
stitution which result from growth or any other cause. 
It is thus, in part, that the assimilation of external food 
by the plant is directed, now more to one class of 
proximate ingredients, as the carbhydrates, and now to 
another, as the albuminoids, although the supplies of 
food presented are uniform both in total and relative 
quantity. 

If a slice of red-beet be washed and put into water, 
the pigment which gives it color does not readily dissolve 



406 HOW CROPS GtROM. 

and diffuse out of the cells, but the water remains color- 
less for several days. The pigment is, however, soluble 
in water, as is seen at once by crushing the beet, where- 
by the cells are forcibly broken open and their contents 
displaced. The cell-membranes of the uninjured root 
are thus ajmarently able to withstand the solvent power 
of water upon the pigment and to restrain the latter 
from diffusive motion. Upon subjecting the slice of 
beet to cold until it is thoroughly frozen, and then plac- 
ing it in warm water so that it quickly thaws, the latter 
is immediately and deeply tinged with red. The sudden 
thawing of the water within the pores of the cell-mem- 
brane has in fact so altered them, that they can no 
longer prevent the diffusive tendency of the pigment. 
(Sachs.) 



4. 



MECHANICAL EFFECTS OF OSMOSE ON" THE PLANT. 

The osmose of water from without into the cells of the 
plant, whether occurring on the root-surface, in the 
buds, or at any intermediate point where chemical 
changes are going on, cannot fail to exercise a great me- 
chanical influence on the phenomena of growth. Root- 
action, for example, being, as we have seen, often suffi- 
cient to overcome a considerable hydrostatic pressure, 
might naturally be expected to accelerate the develop- 
ment of buds and young foliage, especially since, as com- 
mon observation shows, it operates in perennial plants, 
as the maple and grape-vine, most energetically at the 
season when the issue of foliage takes place. Experi- 
ment demonstrates this to be the fact. 

If a twig be cut from a tree in winter and be placed in a 
room having a summer temperature, the buds, before dor- 



MECHANICAL EFFECT OF OSMOSE OX PLANTS. 407 



mant, shortly exhibit signs of growth, 
and if the cut end be immersed in wa- 
ter, the buds will enlarge quite after 
the normal manner, as long as the nu- 
trient matters of the twig last, or until 
the tissues at the cut begin to decay. 
It is the summer temperature which 
excites the chemical changes that re- 
sult in growth. Water is needful to 
occupy the expanding and new-form- 
ing cells, and to be the vehicle for the 
translocation of nutrient matters from 
the wood to the buds. Water enters 
the cut stem by imbibition or capillar- 
ity, not merely enough to replace loss 
by exhalation, but is also sucked in by 
osmose acting in the growing cells. 
Under the same conditions as to tem- 
perature, the twigs which are connected 
with active roots expand earlier and 
more rapidly than cuttings. Artificial 
pressure on the water which is pre- 
sented to the latter acts with an effect 
similar to that which the natural stress 
caused by the root-power exerts. This 
fact was demonstrated by Bo'ehm 
(Sitzungsberichte der Wiener Akad., 
18G3), in an experiment which may be 
made as illustrated by the cut, Fig. 70. 
A twig with buds is secured by means 
of a perforated cork into one end of a 
short, wide glass tube, which is closed 
below by another cork through which 
passes a narrow syphon-tube, B. The 
cut end of the twig is immersed in 
water, IT', which is put under pressure 
by pouring mercury into the upper 



408 HOW CROPS GROW. 

extremity of the syphon-tube. Horse-chestnut and grape 
twigs cut in February and March and thus treated — the 
pressure of mercury being equal to six to eight inches 
above the level, J/— after four to six weeks, unfolded 
their buds with normal vigor, while twigs similarly cir- 
cumstanced but without pressure opened four to eight 
days later and with less appearance of strength. 

Fr. Schulz {KarsterCs Bot. Unters., Berlin, II, 143) 
found that cuttings of twigs in the leaf, from the horse- 
chestnut, locust, willow and rose, subjected to hydro- 
static pressure in the same way, remained longer turges- 
cent and advanced much further in development of 
leaves and flowers than twigs simply immersed in water. 

The amount of water in the soil influences both the 
absolute and relative quantity of this ingredient in the 
plant. It is a common observation that rainy spring 
weather causes a rank growth of grass and straw, while 
the yield of hay and grain is not correspondingly in- 
creased. The root-action must operate with greater 
effect, other things being equal, in a nearly saturated 
soil than in one which is less moist, and the young cells 
of a plant situated in the former must be subjected to 
greater internal stress than those of one growing in the 
latter — must, as a consequence, attain greater dimen- 
sions. It is not uncommon to find fleshy roots, espec- 
ially radishes which have grown in hot.-beds, split apart 
lengthwise, and Hallier mentions the fact of a sound 
root of petersilia splitting open after immersion in water 
for two or three days. {Phytopathologie, p. 87.) This 
mechanical effect is indeed commonly conjoined w T ith 
others resulting from abundant nutrition, but increased 
bulk of a plant without corresponding increase of dry 
matter is doubtless in great part the consequence of large 
supplies of water to the roots and its vigorous osmose 
into the expanding plant. 



APPENDIX. 



Composition of various Agricultural Products giving the Aver- 
age quantities of Water, Nitrogen, Ash, and Ash-ingredients in 
1,000 parts of fresh or air-dry substanees. According to Prof. E. 
von Wolff, 1889. 



< 



i< SI 
Is 5 < 

Ph do 



GRASSKS. 

Rich pasture grass, 

Young grass and after- 
math, 

Orchard grass, 

Rye grass, 

Timothy, 

CLOVERS AND LEGUMES. 

Red clover, young, 

Red clover in bud, 

Red clover in flower,. . . 
Lucern or Alfalfa, in 

early bloom, 

Alsike clover, 

White clover in flower, 
ROOTS, TUBERS, BULBS. 

Beets, 

Carrots, 

Rutabagas, 

Turnips, 

Sugar-beets, 

Radish, 

Parsnip, 

Horseradish, 

Onion, 

Artichoke, Heliaiit/uis,. 
Potato, 

"VEGETABLES." 

Cabbage, loose outer 

leaves, 

Cabbage, heart, 

Cauliflower, heart, 

Cucumber, fruit, 

Lettuce, 

Asparagus, sprouts, 

Spinage, 

Mushrooms, edible, 



782 

800, 
700 
700 
700 

860 1 
820 
800 

740 
820 
805 

880 
850 
870 
920 
815 
933 
793 
7G7 
8G0 
800 
750 



890 
900 
904 
956 
940 
933 
903 
888 



7.2 

5.6 

5.7 
5.4 

6.0 
5.3 
4.8 

7.2 
5.3 
5.6 

1.8 
2.2 
2!l 
1.8 
1.6 
1.9 
5.4 
4.3 
2.7 
3.2 
3.4 



2.4 
3.0 
4.0 
1.6 

3.2 
4.9 
4.7 



SEEDS OF CEREALS. 

Oats, 143 17.6 

Millet, 140 20.3 

M'lize, 14416.0 

Sorghum 140| 

Spring Wheat, 1 143 20.5 

Spring Barley, !l43 16.0 

Spring Rve 143 

Winter Wheat, 144 20.8 

Winter Barley 145 16.0 

Winter Rye. ! 143 17.6 



21.1 

18.1 
17.8 
20.4 

20.5 

14.0 
14.7 
13.7 

19.2 

8.6 

14.3 

9.1 
8.2 
7.5 
G.4 
7.1 
4.9 
10.0 
19.7 
7.4 
9.8 
9.5 



15.6 
9.6 
8.0 
5.8 
8.1 
5.0 
16.0 
10.0 

26.7 
29.5 
12.4 
16.0 
18.3 
22.3 
18.0 
16.8 
17.0 
17.9 



8.1 


1 
0.3 2.6 


5.3 


0.7 2.5 


5.9 


0.8 1.1 


7.1 


0.7 1.5 


7.1 


0.4 1.7 


5.1 


0.3 3.9 


5.5 


0.3 4.5 


4.4 


0.3 4.8 


4.5 


0.3 8.5 


2.4 


0.3 2.9 


3.1 


1.0 4.3 


4.8 


l.s' 0.3 


3.0 


1.7 0.9 


> 3.5 


0.4 0.9 


2.9 


0.6 0.7 


3.8 


0.6 0.4 


1.6 


1.0 0.7 1 


5.4 


0.2 1.1 


7.7 


0.4 2.0 


2.5 


0.2 1.6 


4.7 


1.0 0.3 


5.8 


0.3 0.3 


5.8 


1.5 2.8 


4.3 


0.8 1.2 


3.6 


0.5 0.5 


2.4 


0.6 0.4 


3.7 


0.8 0.5 


1.2 


0.9 0.6 


2.7 


5.7 1.9 


5.1 


0.2 0.1 


4.8 


0.4 1.0 


3.3 


0.4 0.2 


3.7 


0.1 0.3 


3.3 


0.5 0.2 


5.6 


0.3 0.5 1 


4.7 


0.5 0.6 


6.2 


0.3 


5.2 


0.3 0.5 


. 2.8 


0.7 0.1 


, 5.8 


0.3 0.5 



1.2 

1.2 

0.5 
0.4 
0.7 

1.3 
1.6 
1.5 

0.9 
1.1 
1.4 

0.4 
0.4 
0.3 
0.2 
0.6 
0.2 
0.6 
0.4 
0.3 
0.3 
0.5 



0.6 
0.4 
0.3 
0.2 
0.2 
0.2 
1.0 
0.3 

1.9 

2.8 
1.9 
2.4 
2.2 
2.0 
2.2 
2.0 
2.1 
2.0 



1.9 

1.4 
1.3 

2.2 
2.4 

1.7 
1.5 
1.3 

1.6 

0.9 
1.8 

0.8 
1.1 
1.1 

0.8 
0.9 
0.5 
1.9 
2.0 
1.3 
1.4 
1.6 



1.4 
1.1 
1.6 
1.2 
0.7 
0.9 
1.6 
3.4 

6.8 
6.5 
5.7 
8.1 
9.0 
7.8 
9.2 
7.9 
5.6 
8.5 



0.7 

1.0 

0.5 
0.8 
0.6 



4.1 

4.6 

5.9 
6.5 
6.6 



0.3| 0.4 

0.4 0.4 
0.4 0.4 



1.1 
0.4 
1.1 

0.3 
0.5| 
0.7 
0.7 
0.3 
0.3 
0.5 
4.9 
0.4 
0.6 
0.6 



2.4 
1.3 
1.0 
0.4 
0.3 
0.3 
1.1 
0.4 



1.8 
0.3 
0.6 

0.2 
0.2 
0.1 
0.1 
0.2 

0.2 
1.5 
0.7 
0.2 
0.2 



0.1 
0.1 
0.3 
0.5 
1.3 
0.5 
0.7 
0.1 



0.5 10.5 
0.1 15.6 
O.lj 0.3 
I 1.2 
0.3 
5.8 
0.2 
0.3 
4.9 
0.3 



0.2 

0.4 

0.1 
0.5 
0.2| 

r 9 



2.1 

1.1 
1.3 
2.1 
1.1 

0.6 
0.5 
0.5 

0.6 
0.5 
0.6 

0.9 
0.4 
0.5 
0.3 
0.3 
0.5 
0.4 
0.3 
0.2 
0.4 
0.3 



1.3 
0.5 
0.3 
0.4 
0.4 
0.3 
1.0 
0.1 

0.3 
0.1 
0.2 

0.1 
0.2 

0.1 

0.1 



410 



HOW CEOPS GROW. 



Composition of various Agricultural Products.— [Continued.] 





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32 


02 



SEEDS OF LEGUMES AND 
CLOVERS. 

Horse bean, Vicia, 

Garden bean, Phaseolus, 

Soy bean, 

Pea, 

Red Clover, 

White Clover, 

OIL SEEDS. 

Cotton, 

Hemp, 

Flax, 

Mustard, 

fruits. 

Apple, entire fruit, 

Pear, entire fruit, 

Cherry, entire fruit, — 
Plum, entire fruit, ...... 

Grape, entire fruit 

HAY. 

Alpine hay, 

From very 'young grass, 
From young grass and 

aftermath, 

From cereals cut in 

bloom, 

English rye grass, 

Red Clover, young, 

Red Clover in bud, 

Red Clover in flower,.. 

Red Clover, ripe, 

White Clover in flower, 

Alsike Clover, 

Lucern (Alfalfa) early 

bloom, 

STRAW. 

Oat, 

Barley, 

Maize, 

Spring Wheat, — 

Winter Wheat, 

Winter Rye, 

Buckwheat, 

Pea, 

CHAFF, ETC. 

Oat Chaff, 

Rve Chaff, 

Wheat Chaff, 

Corn Cobs, 



145 
150 
100 
143 
150 
150 

77 
122 
118 
130 

831 

831 
825 
838 
830 

150 
150 



40.8 
39.0 
53.4 
35.8 
30.5 



36.5 
26.1 

32.8 



0.6 
0.6 



31.0 
27.4 
28.3 
23.4 
38.3 
33.8 

33.8 
46.3 
32.6 
36.5 

2.2 

3.3 

I 3.9 

I 2.9 

1.7 8.8 



18.5 
25.5 



29.7 
82.4 



1601 19.1 76.0 



150 
143 
167 
165 
160 
150 
165 
160 

160 

143 
143 
150 

] 43 
143 
143 
160 

100 

143 
143 

143 

140 



16.3 
35.5 
24.5 
19.7 
12.5 
23.2 
24.0 



59.4 
58.2 
82.3 
68.4 
57.6 
44.7 
61.1 
40.0 



23.0 62.0 



5.6 
6.4 
4.8 
5.6 
4.8 
4.0 
13.0 
10.4 

6.4 
5.8 
7.2 
2.3 



61.6 
45.9 
45.3 
38.1 
46.0 
38.2 
51.7 
43.1 

71.2 

82.7 

92.0 

4.5 



MISCELLANEOUS. 

Tobacco leaves, |180 34.8 140.7 

Tobacco stems, ! 180' 24.6 64.7 

Flax stalks, !l20l J 31.1 

Hemp stalks !l08| | 31.7 

Hops, entire plant, !140 25.0 72.9 

Cottonseed Cake, 1112 62.1 66.4 

Linseed Cake, 1122 47.2 51.3 



12.9 


0.3 1.5 


12.1 


0.4 1.5 


12.6 


0.3 1.7 


10.1 


0.2 1.1 


13.5 


0.4 2.5 


12.3 


0.2 2.5 


10.9 


2.3 1.9 


9.4 


0.4 10.9 


10.0 


0.7 2.6 


5.9 


2.0 7.0 


0.8 


0.6 0.1 


1.8 


0.3 0.3 


2.0 


0.1 0.3 


1.7 


1 0.3 


5.0 


0.1 1.0 


7.7 


0.4 7.1 


31.6 


1.3 10.1 


22.3 


3.0 10.4 


19.3 


1.0 3.4 


20.2 


2.0 4.3 


29.7 


1.9 23.5 


25.3 


1.4 20.7 


18.6 


1.1 20.1 


10.0 


1.4 15.8 S 


13.1 


4.4 18.4 


11.1 


1.2 13.6 


14.6 


1.1 25.2 


16.3 


2.0 4.3 


10.7 


1.6 3.3 


16.4 


0.5 4.9 ! 


11.0 


1.0 2.6 


6.3 


0.6 2.7 


8.6 


0.7 3.1 


24.2 


1.1 9.5 


9.9 


1.8 15.9 


4.5 


2.9 4.0 


5.2 


0.3 3.5 


8.4 


1.7 1.7 


2.3 


0.1 0.2 i 


40.9 


1 
4.5 50.7 ! 


28.2 


6.6 12.4 


9.7 


2.5 6.9 


5.5 


0.6 16.8 


17.9 


1.9 19.7 


15.8 


1 2.9 


12.5 


0.8 4.3 I 



2.2 
2.1 
2.5 
1.9 
4.9 
3.9 

5.6 
2.6 
4.7 
3.7 

0.2 
0.2 
0.2 
0.2 
0.4 

2.4 
4.6 

5.1 

1.7 
1.3 

7.6 
7.6 
6.3 
6.9 
5.8 
5.0 

3.1 

2.3 
1.2 
2.6 
0.9 
1.1 
1.2 
1.9 
3.5 

1.5 
1.1 
1.2 
0.2 

10.4 
0.5 
2.0 
2.1 
7.0 

10.1 
8.1 



12.1 
9.7 

10.4 
8.4 

14.5 

11.6 

10.5 
16.9 
13.5 
14.6 

0.3 
0.5 
0.6 
0.4 
1.4 

2.7 
7.4 

5.9 

5.6 

6.2 
10.0 
6.9 
5.6 
4.4 
7.8 
4.1 

5.3 

2.8 
1.9 
3.8 
2.0 
2.2 
2.5 
6.1 
3.5 

1.3 
5.6 
4.0 
0.2 

6.6 

9.2 
4.2 
2.1 
5.8 
30.5 
16.2 



1.1 
1.1 

0.8 
0.8 
0.9 
1.6 

0.7 

0.1 
0.8 
1.8 



0.2 
0.2 

0.2 
0.5 
0.8 

0.1 
5.5 
0.4 
0.9 



0.1 0.1 

0.2 1 0.1 

0.2, 0.4 

0.1 0.1 

0.5 1 0.3 

1.4 7.2 
2.7,15.9 

4.119.4 

1.5 24.7 
2.3 18.5 



1.8 
1.7 
1.9 
1.4 
4.5 
1.6 

3.6 



2.5 
1.8 
1.6 
3.0 
2.7 
1.6 

5.9 



2.0 28.8 
1.8 23.4 
2.4 13.1 
1.2 18.2 

1.1 31.0 
1.6 18.8 



2.7 
2.7 



2.9 
2.9 



3.5 50.4 

0.1 66.4 

74.7 



0.1 

8.5 
2.2 
2.0 
0.6 
2.9 13.3 
0,8| 5.5 
1.7! 6.4 



1.3 

8.1 
1.6 
1.7 
3.1 



INDEX. 



Absorption by the root, 260, 269, 272 
Access of air to interior of 

Plant, 313 

Afcetic Acid 76 

Acetamicle, 115 

Acids, Definition of 81 

Acids, Test for 82 

Acid elements, 127 

Acid-proteids, 99 

Adhesion, 9,388 

Agriculture, Art of 1 

Agricultural products, Compo- 
sition in 1,000 parts, . . . 409 
Agricultural Science, Scope of . 7 
Air-passages in plant, .... 313 

Air-roots, 273 

Akene, 331 

Albumin, 89 

Albuminates, 99 

Albuminoids, Characters and 

composition, . . .87, 104, 106 
Albuminoids in animal nutrit- 
ion, 108 

Albuminoids, Diffusion of . . .403 
Albuminoids in oat-plant, . . 234 
Albuminoids, Mutual relations 

of 107 

Albuminoids, Proportion of, in 
vegetable products, . . . 114 

Albumose, 101 

Alburnum 305 

Aleurone, 110 

Alkali-earths, 81, 139 

Alkali-earths, Metals of . . .139 

Alkali-metals, 138 

Alkalies, 81, 138 

Alkali-proteids, 99 

Alkaloids, 120 

Allylsulphocyanate, 129 

Alumina, 143 

Aluminium, 143 

Aluminium phosphate, .... 28 

Amides 114, 118 

Amido-acids, 114, 118 

Amidoacetic acid, 115 

Amidocaproic acid, 116 

Amidovaleric acid, 116 

Amidulin, 52 

Amines, 119 

Ammonium Carbonate, ... 33 
Ammonium Salts in plant, 82, 113 
Amvlan, . . . • 62^ 

411 



Amyloid, 43 

Amylodextrin, 53 

Amyloses, 39, 40 

Anhydrous phosphoric acid, . 132 
Anhydrous sulphuric acid, . .130 

Anther 318 

Apatite, 148 

Arabic acid, 58 

Arabin, 58 

Arabinose, 65 

Arrow root, 48 

Arsenic in plants, . . . 137, 210 
Ash-ingredients, .... 126, 161 
Ash-ingredients, Excess of . . 201 
Ash-ingredients, Excess of, how 

disposed of, 203 

Ash-ingredients, Function of in 

plant, 210 

Ash-ingredients, State of, in 

plant, 207 

Ash of plants, 13, 126 

Ash of plants, Analyses, Tables 

of 164 

Ash of plants, Composition of, 

normal, 177 

Ash of plants, Composition of, 

variations in 151 

Ash, Proportions of, Tables, . .152 

Asparagin, 116 

Assimilation, 364 

Atmosphere, Offices of ... . 367 

Atoms, 30 

Atomic weight, 31 

Avenin, 120 

Bark, 291, 297 

Barium in plants, 210 

Bases, Definition of 81 

Bast-cells, Bast-tissue, 293, 295, 297 
Bean, Leaf, Section of . . . .308 

Bean, Seed, 334 

Berry, 331 

Betain, 116 

Biology, 10 

Bleeding of vine, .... 271, 37J 

Blood-fibrin, 91 

Bone-black, . 15 

Boron, Boric acid, 210 

Buds, Structure of 283 

Buds, Development under pres- 
sure, 406 

Bulbs, 289 

Butyric acid, 76 



412 



HOW CROPS GROW. 



Caesium, Action on oat, . . .209 

Caffein, 117 

Calcium, . .139, 214 

Calcium, carbonate, 145 

Calcium, hydroxide, .... 143 

Calcium, oxide, 139 

Calcium, phosphate, . . .28, 148 
Calcium, sulphate, .... .146 

Callous, 382 

Calyx, 317 

Cambium, 294, 295, 299 

Cane-sugar, 65 

Capillary attraction 389 

Carbamide, 115 

Carbhydrates, 39 

Carbhydrates, Composition . . 72 
Carbhydrates, Transformations 

of 70 

Carbon, Properties of .... 14 

Carbon in ash, 128 

Carbon dioxide, 128 

Carbonates, 128, 144 

Carbonate of lime, 145 

Carbonate of potash, 144 

Carbonate of soda, 144 

Carbonic acid, 19, 128 

Carbonic acid as food of plant, 328 
Carbonic acid in ash-analyses, 149 

Carboxyl, 75, 77 

Casein, 84 

Caseose, 101 

Cassava, 51 

Causes of motion of juices, . .385 

Cell-contents, 249 

Cell-multiplication, 252 

Cell, Structure of 245 

Cells, Forms of 247 

Cellular plants, 243 

Cellular tissue, 255 

Cellulose, 40 

Cellulose, Composition .... 44 
Cellulose, Estimation .... 45 

Cellulose nitrates, 43 

Cullulose sulphates, 43 

Cellulose, Test for 44 

Cellulose, Quantity of, in plants, 46 

Chemical affinity, 29 

Chemical affinity overcome by 

osmose, 403 

Chemical combination, ... 29 
Chemical decomposition, ... 30 

Chemistry, 10 

Chlorides 133, 149 

Chloride of ammonium, decom- 
posed by plant, 184 

Chlorine, 132 

Chlorine essential to crops ? . .194 
Chlorine, function in plant, . 218 
Chlorine in strand plants, . .191 

Chlorophyl, 124, 307, 308 

Chlorophyl requires iron, . . 220 

Chlorophyllan, 125 

Choline, 119 

Circulation of sap, 369 

Citric acid, 80 

Citrates, 80, 149 

Classes of plants, 329 

Classification botanical, . . .329 



Clover, washed by rain, ... 204 

Colloids 392 

Conglutin, 95, 97 

Combustion, 18 

Composite plants, 330 

Concentration of plant-food, .185 
Concretions in plant, .... 205 

Coniferous plants, 330 

Copper in plants, 210 

Cork, 298 

Corm, 288 

Corolla 317 

Cotyledon, 290,333 

Coniferous plants, 330 

Cryptogams, 315,329 

Crystalloid aleurone, . . . .111 

Crystalloids, 392 

Crystals in plant, 206 

Culms, 284 

Cyanides, ....... 127, 129 

Cyanogen, 129 

Definite proportions, Law of . .30 

Density of seeds 339 

Depth of sowing, 355 

Dextrin, 53 

Dextrose, 63 

Diastase, 67, 103, 360 

Diffusion of liquids, .... .390 

Dioecious plants, 318 

Drains stopped by roots, . . .276 

Drupe, 331 

Dry weather, Effect of, on 

plants, 157 

Ducts, 255,294 

Dulcite, 74 

Dundonald's treatise on Agri- 
cultural Chemistry, ... 4 

Elements of Matter, 8 

Embryo, 333 

Endogens, 259, 290, 334 

Endosmose, 394 

Endosperm, 332 

Enzymes, 103 

Epidermis, 291 

Epidermis of leaf, 308 

Eremacausis, 20 

Excretions from roots, .... 280 
Exhalation of water from foli- 
age, 309 

Exogens, .... 239, 293, 296, 334 

Exosmose, 394 

Exudation of ash-ingredients, 203 

Eyes of potato, 289 

Families, 328 

Fatty acids, 75 

Fats, 83 

Fats converted into starch, . . 358 

Fat in oat crop, 230 

Fat in Vegetable Products, . . 87 

Ferments, 102 

Ferric oxide, 142 

Ferric hydroxide, 142 

Ferric salts, 142 

Ferrous oxide, 141 

Ferrous hydroxide, 141 

Ferrous salts, 142 

Fertilization, 319 

Fibrin 91,96 



INDEX. 



413 



Fibrinogen, 91, 96 

Flax fiber, Fig., 41,248 

Flax seed mucilage, ... 58, 62 

Flesh fibrin, 92 

Flower, 317 

Flow of sap, 371 

Fluorine in plants, 209 

Foliage, Offices of 314 

Food of Plant, 366 

Formative layer, 245 

Formulas, Chemical, . . .33, 73 

Fructification, 319 

Fructose, 63 

Fruit, 330 

Galaetin, 61 

Galactose, 65 

Gases, how distributed through- 
out the plant, 404 

Gelatinous Silica, 136 

Genus ; Genera 328 

Germ, 333 

Germination 349 

Germination, Conditions of . .351 
Germination, Chemical Physi- 
ology of 357 

Girdling, 383 

Glauber's Salt, 146 

Gliadin, 92 

Globulin, 96 

Glucoses, 39, 63 

Glucosides, 69 

Glutamin, 116 

Gluten, 92 

Gluten-Casein, 93, 95 

Glycerin, 86 

Glycogen 56 

Glycocoll 116 

Glycollic acid, 77 

Gourd fruits, 331 

Grains, 331 

Grape Sugar, 63 

* Growth, 252 

Growth of roots, 256 

Gum, Amount of, in plants, . . 62 

Gum Arabic, 57 

Gum Tragafcanth, 57 

Gun Cotton 43 

Gypsum, 147 

Haemetin, 110 

Haemoglobin, 109 

Hallett's pedigree wheat, .158, 344 

Hybrid, Hybridizing, 324 

Hydration of membranes, . . 396 
Hydrochloric acid, .... 23, 133 

Hydrocyanic acid, 129 

Hydrogen, 22, 112 

Hydrogen chloride, 23 

Hydrogen sulphide, ... 26, 129 

Imbibition 386 

Imides, 117 

Inorganic matter, 12 

Internodes, 284 

Inulin, 55 

Invertin, 103 

Iodine in plants, .... 134, 210 

Iodine, Solution of 44 

Iron, 141,192 

Iron, Function of 219 



Isomerism, 73 

Juices of the Plant, 369 

Lactic Acid, 77 

Lactose, 68 

Latent buds, 285 

Latex, 304 

Layers, 286 

Lead in plants, 210 

Leaf pores, 309 

Leaves, Structure of . . . 306, 308 
Leaves, office in nutrition, . .828 

Lecithin, 122 

Legume, &32 

Legumin, 95 

Leguminous plants, 332 

Leucin, 116 

Levulin, *. . 56 

Levulose, 63 

Lignin, 41 

Lime, 139 

Liquid Diffusion, 390 

Lithia, Lithium, in plants, . .209 
Lupanin, Lupinin, Lupinidin, 120 

Magnesia, 140 

Magnesium, 140, 215 

Magnesium hydroxide, . . . .141 

Magnesium oxide, 140 

Maize fibrin, 93 

Malates, 149 

Malic acid, 79 

Malonic acid, 79 

Malt, Chemistry of 358 

Maltose, 67 

Manganese, 142, 193 

Mannite, 74 

Mannose, 65 

Margarin, 85 

Medullary rays, 299 

Membrane-diffusion, . . 393, 397 
Membranes, Influence on mo- 
tion of juices 404 

Metals, Metallic elements, . .138 

Metapectic acid, 59 

Metarabin, 59 

Milk ducts, 304 

Milk Sugar, 68 

Molecules, Molecular Weights, 32 

Monaecious plants, 319 

Motion caused by adhesion, . .389 

Mucedin, 92, 321 

Multiple Proportions, .... 32 

Muriate of potash, 140 

Muriatic acid, 133 

Myosin, 97, 98 

Nectar, Nectaries, 319 

Neurin, 120 

Nicotin, 120 

Niter, Nitrate of potassium, . . 149 
Nitrates in plants, .... 113, 149 

Nitric Acid in plant, 113 

Nitrogen, Properties of . . . .20 

Nitrogen in ash, 127 

Nodes, 284 

Non-metals, 127 

Notation, Chemical 33 

Nuclein, 122 

Nucleus, 300 

Nut, 331 



414 



HX)W CROPS GROW. 



Nutrient matters in plant, Mo- 
tion of 401 

Nutrition of seedling, . . . .357 

Nutrition of plant, 366 

Oat plant, Composition and 

growth of 223 

Oats, weight per bushel, . . .176 

Oil in seeds, etc., 83 

Oil of vitriol, 26, 130 

Oils, Properties of 83 

Oleic acid, 86 

Olein, 85 

Orders 328 

Organic matter, 12 

Organism, Organs, 243 

Osmose, ~ . . . 393 

Osmose, mechanical effects on 

plant, 406 

Osmometer, 394 

Ovaries, 318 

Ovules, 318 

. Oxalates, 78, 149 

Oxalic acid, 78 

Oxides, 19, 20 

Oxides of iron, described, . 19, 141 
Oxides of manganese, described 142 

Oxyfatty acids, 77 

Oxygen, Properties of .... 16 
Oxygen occurrence in ash, . .128 
Oxygen in Assimilation, . . . 364 
Oxygen in Germination, . . .353 

Palmitic acid, 86 

Palmitin, 85 

Papain, 104 

Parenchyma, 255 

Papilionaceous plants, . . . 330 

Pappus, 331 

Pararabin, 59 

Paraglobulin, 96, 99 

Paragalactin, 61 

Pectic acid, 74 

Pectin bodies, 58, 59, 74 

Pectosic acid 74 

Pectose, 58, 61, 74 

Pedigree wheat, 158, 344 

Pepsin, 104 

Peptones, 100 

Permeability of cells, .... 253 

Petals, 318 

Phanerogams, Phaen ogams ,316, 329 

Phloridzin, 69 

Phosphate of lime, 148 

Phosphate of soda, 148 

Phosphate of potash, . . . .147 

Phosphates 28, 132, 147 

Phosphates function in plants, 211 
Phosphates relation to albu- 
minoids, 221 

Phosphoric acid, 27, 132 

Phosphorite, 148 

Phosphorized substances, . . 122 

Phosphorus, 27 

Phosphorus pentoxide, . . 27, 132 

Physics, 10 

Physiology, 10 

Piperin, 121 

Pistils, 318 

Pith, 297 



Pith rays, 299 

Plastic Elements of Nutrition, 109 

Plumule, 333 

Pollarding, 286 

Pollen 318 

Polygonum convolvulus, Fertil- 
ization of, Fig., 295 

Pome, 331 

Porosity of vegetable tissues, .385 
Potato leaf, Pores of, Fig., . . 309 
Potato stem, Section of, Fig., .304 
Potato tuber, Structure and Sec- 
tion of, Fig., 300 

Potash, 138, 144 

Potash lye, 139 

Potassium, ....... 138, 211 

Potassium carbonate, . . . .144 

Potassium Chloride 149 

Potassium hydroxide, . . . .139 

Potassium oxide, 138 

Potassium phosphate, . . . .147 
Potassium silicate, ..... 134 

Potassium sulphate, 146 

Prosenchyma, 255 

Protagon, 123 

Proteoses, loo 

Protoplasm, 245 

Protein bodies, or Proteids, . . 87 
Proximate Principles, .... 37 

Quack grass, 287 

Quantitative relations among 
ingredients of plant, . . .220 

Quartz, 134 

Quince seed mucilage, .... 62 

Radicle, 333 

Rafflnose, 68 

Reproductive Organs, . . 243, 315 

Rhizome, 287 

Rind 297 

Rock Crystal, 134 

Root-action, imitated, . . . .400 
Root-action, Osmose in . . . 399 

Root cap, 257 

Root distinguished from stem, 258 

Root excretions, 280 

Root hairs, . ... \ ... 265 
Root, Seat of absorptive force 

in, 270, 399 

Root stock, 287 

Rootlets, 260 

Roots, Growth of 256 

Roots contact with soil, . . . 266 
Roots going down for water, . .276 
Roots, Search of food by . . .263 

Roots, Quantity of 263 

Rubidium action on oat, . . . 209 

Runners, , 286 

Saccharose, 60 

Sacch arose, Amount of, in 

plants, 66 

Sago, -51 

Salicin, 69 

Salicornia, 191 

Sal-soda, 145 

Salsola, . 191 

Salts, Definition of 81 

Salts, in ash of plants, . . . .143 
Saltwort, 191 



INDEX. 



415 



Samphire, 191 

Bap, 369 

Sap, Acid and alkaline . . . .378 

Sap ascending, 379,384 

Sap descending, 382 

Sap, Composition of 376 

Sap of sunflower, 378 

Sap, Spring flow of . . . , . 370 

Sap wood, 305 

Saponification, 85 

Saxifraga crustata, 206 

Seed, .' 332 

Seed vessel, 330 

Seed, Ancestry of 346 

Seeds, constancy of compositionl45 

Seeds, Density of 339 

Seeds, Weight of 340 

Seeds, Water imbibed by . . . 399 
Selective power of plant, . . .401 

Seminose, 65 

Sepals, 317 

Sieve-cells, 303 

Sieve-cells in pith, .... 343, 345 

Silica, 134 

Silica entrance into plant, . .402 
Silica, Function of, in plant, . 216 

Silica in ash, 197 

Silica in textile materials, . . 200 
Silica unessential to plants, . .197 

Silicates, 134 

Silicate of potassium, . . . .134 

Silicic acids, 135 

Silicon, 134 

Silicon, Dioxide 134 

Silk of maize, 319 

Silver-grain, 299 

Sinapin, 120 

Soaps, 93 

Sodium, 139 

Sodium carbonate, 144 

Sodium essential to ag. plants? 186 

Sodium hydroxide, 139 

Sodium in strand and marine 

plants, • .191 

Sodium oxide, 139 

Sodium sulphate, 146 

Sodium, Variations of, in field- 
crops, 188 

Sodium Chloride, 149 

Soil. Offices of 368 

Solanin, 121 

Solution of starch in Germina- 
tion, 358, 361 

Soluble silica, 135 

Soluble starch, 52 

Species, 326 

Spirits of salt, 133 

Spongioles, 257 

Spores, 316 

Sports 327 

Stamens, 318 

Starch, amount in plants, . . 51 

Starch-cellulose, 50 

Starch estimation, 52 

Starch in wood, 373, 376 

Starch, Properties of .... 47 

Starch, Test for 49 

Stearic acid, 86 



Stearin, 85 

Stem, Endogenous 290 

Stem, Exogenous 2'.)6 

Stem, Structure of 289 

Stems, 282 

Stigma, 318 

Stomata, 309 

Stool, 287 

Suckers, 287 

Sucroses, 39, 65 

Sugar, Estimation of 65 

Sugar, in cereals, 69 

Sugar in Sap, 377 

Sugar of milk, 68 

Sulphate of lime, 146 

Sulphate of potash, 146 

Sulphate of soda, 146 

Sulphates 26, 131, 146 

Sulphates, Function of . . . .210 
Sulphates reduced by plant, . 208 

Sulphides, 26, 130 

Sulphide of potassium, . . . .130 

Sulphites, 129 

Sulphur, 25, 129 

Sulphur in oat, 208 

Sulphur dioxide, 25, 130 

Sulphureted. hydrogen, . .26, 115 

Sulphurets, 26 

Sulphuric acid, 26, 130 

Sulphuric acid in oat, . . . .208 
Sulphuric oxide (S0 3 ), .... 209 
Sulphur trioxide (S0 3 ), . . .25, 130 

Sulphurous acid, 25, 129 

Symbols, Chemical 31 

Tao-foo, 96 

Tapioca, 51 

Tap-roots, 259 

Tartaric acid, 80 

Tartrates, 80 

Tassels of maize, 319 

Theobromin, 118 

Tillering, 287 

Titanic acid, 137 

Titanium, 137, 209 

Translocation of substances in 

plant, 237 

Trypsin 104 

Tubers, 273, 288 

Tuscan hat- wheat, 158 

Tyrosin, 116 

Ultimate Composition of Vege- 
table Matters, 13, 29 

Umbelliferous plants, .... 330 
Unripe seed, Plants from . . .338 

Urea, 115 

Valence, 35 

Varieties, 158, 326, 327 

Vascular bundle of maize 

stalk, 291, 293 

Vascular-tissue, 255 

Vegetable acids, 75 

Vegetable albumin, 90 

Vegetable casein, 94 

Vegetable cell, 243 

Vegetable fibrin, 92 

Vegetable globulins, 97 

Vegetable mucilage, 57 

Vegetable myosins, 98 



416 



HOW CROPS GROW. 



Vegetable parchment, .... 44 

Vegetable tissue, 246 

Vegetative organs, 243 

Vernin, 118 

Vicin, 120 

Vitality of roots, 282 

Vitality of seeds, 335 

Vitellin, 96 

Water, Composition of . . . .37 
Water, Estimation of .... 39 
Water, Formation of .... 24 
Water in air-dry plants .... 39 
Water in fresh plants, .... 38 
Water in vegetation, Free ... 39 
Water in vegetation, Hygro- 
scopic 39 



Water-oven, 38 

Water-culture 181 

Water-glass, 135 

Water Roots 273 

Wax, 83 

Wood, 41, 305 

Wood cells, 293 

Wood cells of conifers, . . . .301 

Woody stems, 305 

Woody tissue, 255 

Xylin, 61 

Xylose 62 

Yeast, 103 

Zanthophyl, 125 

Zein, 93 

Zinc, 210 



HOW CROPS FEED. 

A TREATISE ON THE 

ATMOSPHERE AND THE SOIL 

AS RELATED TO THE 

NUTRITION OF AGRICULTURAL PLANTS. 

• With Illustrations. 

BY 

SAMUEL W. JOHNSON, M.A., 

Professor of Analytical and Agricultural Chemistry m the Shef- 
field Scientific School of Yale College ; Chemist to the Con- 
necticut State Agricultural Society ; Member of 
the National Academy of Sciences. 



The work entitled "How Crops Grow " has been received with very great 
favor, not only in America, but in Europe. The Author, therefore, puts forth 
this volume— the companion and complement to the former— with the hope 
that it also will be welcomed by those who appreciate the scientific aspects 
of Agriculture, and are persuaded that a true Theory is the surest guide to a 
successful Practice. In this, as in the preceding volume, the Author'* method 
has been to bring forth all accessible facts, to present their evidence on the 
topics under discussion, and dispassionately to record their verdict. If this 
procedure be sometimes tedious, it is always safe, and there is no other mode 
of treating a subject which can satisfy the earnest inquirer. It is, then, to all 
Students of Agriculture, whether on the Farm or in the School, that this vol- 
ume is specially commended. 

CONTENTS. 

DIVISION I. 

The Atmosphere as Related to Vegetation. 

CHAPTER I.— Atmospheric Air as Food of Plants. 

CHAPTER II. — The Atmosphere as Physically Related to Vegetation. 

DIVISION II. 

The Soil as Related to Vegetable Production. 

CHAPTER I.— Introductory. 

CHAPTER II.— Origin and Formation of Soils. 

CHAPTER III.— Kinds of Soils, their Definition and Classification. 

CHAPTER IV.— Physical Characters of the Soil. 

CHAPTER V.— The Soil as a Source of Food to Crops: Ingredients 

whose Elements are of Atmospheric Origin. 
CHAPTER VI.— The Soil as a Source of Food to Crops Ingredients 

whose Elements are Derived from Rocks. 

Price, post-paid, $2. 

ORANGE JUDD COMPANY, 

751 Broadway, New-York. 



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